In looking at the words, forever, everlasting and eternal in English bible translations, the place to start is with the Greek word "aionios". Why? Because it is the next step back in the sequence following these three words to the original thought of the speakers of the words. The goal in ALL translation efforts is "to communicate the thought of the speaker in the time that he/she spoke/wrote".
Too many people are willing to accept the meanings of words that have morphed or been mistranslated over centuries. Then they formulate doctrine, blinding the understanding of great masses of people who take their word for it. The second step in looking at the words "forever, everlasting and eternal" is to look at the Hebrew/Aramaic word "olam". "Olam" is the key, because it is the word that most accurately communicates what the speakers thought- olam being a Hebrew word communicating the thoughts of the original Hebrew speakers. This is especially true as regards Jesus and Paul because we know the words they spoke/wrote were "pre-eminently" based in Hebrew thought and spirituality. Paul called himself a Hebrew of Hebrews. Jesus hardly spoke a word that did not echo or directly quote the words of the Hebrew prophets that were before him.
In looking at "olam" we will look at both the contemporary Jewish understanding of the word, and the contextual use of the word in antiquity- primarily from the scriptures. A modern view of olam as a Jewish word helps us understand where it has arrived in thought/meaning, less encumbered by Roman and Western(English) mutation.
Let's look at some of these modern usages.
Tikkun olam (Hebrew: תיקון עולם) is a Hebrew phrase that means "repairing the world." The phrase is included in the Aleinu, a Jewish prayer said to have been written by the Biblical Joshua. In Judaism, the concept of tikkun olam originated in the early rabbinic period(first 3 centuries AD). The concept was given new meanings in the kabbalah of the medieval period and further connotations in modern Judaism.[Wiki:(1)Social responsibility in Jewish thought and law:Shatz,Waxman,Diament,1997]
ʿolam ha-ba, ( Hebrew: “the world to come”) in Jewish theology, either “the world after death” or the new creation or restoration of the world that is to follow the messianic millennium. Because this latter interpretation stemmed from the teachings and exhortations of the prophets, it was especially prevalent during the period of the Second Temple of Jerusalem (516 bc–ad 70). (Encyclopedia Brittanica)
ʿolam ha-ze, (Hebrew: “this world”), in Jewish theology, present life on earth, as opposed to ʿolam ha-ba (“the world to come”). Though ʿolam ha-ze is full of misery and injustice, one’s view of life is transformed by realizing—as the Mishna (code of Jewish law) explains—that “this life” is but an antechamber where one prepares oneself to be admitted to the banquet hall that is “the world to come.”(Encyclopedia Britannica)
In these usages of the word 'olam' we see the translation as "world". However, this also includes a meaning related to time, as in epoch, or aion, or age; in that the "world" spoken of is related to the ages, such as are commonly referred to in English or western thought as "other worldly" or "the world to come" or "the ancient world". Specificly, olam in these instances is defined by the characteristics of the time connected to it, such as ha-ze or ha-ba. This meaning is consistent with the new testament translations to some extent, in that they translated "aion"(greek, from Olam) , in its various forms, into both "world" and "age", as well as "forever" and "eternal". In the OT the word Olam is always defined contextually by the subject it is associated with. In one place it means "world to come", in another it means "an indefinite term defined by certain unpredictable circumstance", such as a slave being indentured "olam"(as long as he lives). When coupled with references to God, it means forever, because God transcends time entirely. We call the realm of God eternal, and it is. Hebrews called the realm of God "olam"- another world, indefinite because of it being beyond our sphere of knowledge, eternal only when defined contextually by its association with the ALMIGHTY. In all these things, "olam" is an indefinite expression- a away of relating various dimensions of the unknown or indefinable. This returns to the original definition, "beyond the horizon", "the grey", "other world". That the word is not strictly "world" is implicit in that the words "and he shall be your slave olam" could clearly make no sense if rendered world. In this instance it is a word that defines indefinite time. From this, one might conclude, that is someone was to say, "You shall be punished 'olam', it might not mean forever without end, but rather until the time specified (you shall not escape until you have paid the last penny, few stripes, many stripes, etc, all concepts relating to limited redemptive judgment rather than eternal torment). In the Old Testament the word olam is used 413 times, many of which CANNOT mean, because of the context, forever without end. For instance, Genesis 6:4
There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old(olam), men of renown.
In this place olam does not mean forever. It is looking back into antiquity. It says, essentially, "the same were the mighty men of the world long ago, in a time clouded by distance."
Another example: Exodus 19:9
The LORD said to Moses, "I am going to come to you in a dense cloud, so that the people will hear me speaking with you and will always(olam) put their trust in you." Then Moses told the LORD what the people had said.
Here olam has an indefinite meaning. It refers to the nature of the relationship between Moses and the people of Israel, meaning, essentially, "For as long as you are speaking to themm as long as you live". Obviously, Moses time of speaking for God to Israel came to an end upon his death, and although he still speaks through the scriptures- clearly God was speaking in reference to the time of Moses' earthly ministry to the sons of Jacob.
One last such example, and there are many more, is:
...then you shall take an awl and pierce it through his ear into the door, and he shall be your servant forever(olam). (Deu 15:17NASB)
Here, olam is an indefinite period with a definite ending point- the life time of the servant. The New International Version translates it this way
....then take an awl and push it through his ear lobe into the door, and he will become your servant "for life"(olam). (Deu 15:17NIV)
It seems we may regard as dubious any assertion that 'aionios' always means 'forever without end'. since 'aionios' is a Greek translation from the word 'olam', which we can CLEARLY see does not always mean for ever, eternal, or everlasting. From this fact, we can also clearly see that theologians make confident but unstudied claims about translation issues in order to support their theological assumptions and preferences.
‘Olam (Hebrew) ‘Ōlām Ulom (Phoenician) [from ‘ālam to hide, conceal] Also oulom. Long duration, long past time, great antiquity, hence occasionally used for the future; again, the world. Parallel to the Gnostic Aeon, which signifies a time period, something secret and esoteric, and the world which exists in the time period; also parallels the Sanskrit kala. Sometimes mistranslated as eternity. Frequently used in the plural (‘olamin).(Encyclopedic Theosophical Glossary)
Perhaps the reason for the inconsistency is that there is no word in English that really incorporates the Hebrew mindset expressed in "olam". In such cases, the translators would have served us better had they simply used the original word, "olam". The best explanation of this is contained in an article by Jeff Benner of the Ancient Hebrew Research Institute.
Ancient Hebrew Word Meanings
Eternity ~ olam
By Jeff A. Benner
Ancient Hebrew Research Center
"In the ancient Hebrew words that are used to described distance and direction are also used to describe time. The Hebrew word for east is qedem and literally means "the direction of the rising sun". We use north as our major orientation such as in maps which are always oriented to the north. While we use the north as our major direction the Hebrews used the east and all directions are oriented to this direction. For example one of the words for south is teyman from the root yaman meaning "to the right". The word qedem is also the word for the past. In the ancient Hebrew mind the past is in front of you while the future is behind you, the opposite way we think of the past and future. The Hebrew word olam means in the far distance. When looking off in the far distance it is difficult to make out any details and what is beyond that horizon cannot be seen. This concept is the olam. The word olam is also used for time for the distant past or the distant future as a time that is difficult to know or perceive. This word is frequently translated as eternity or forever but in the English language it is misunderstood to mean a continual span of time that never ends. In the Hebrew mind it is simply what is at or beyond the horizon, a very distant time. A common phrase in the Hebrew is "l'olam va'ed" and is usually translated as "forever and ever" but in the Hebrew it means "to the distant horizon and again" meaning "a very distant time and even further" and is used to express the idea of a very ancient or future time."
Perhaps the reason for the inconsistency is that there is no word in English that really incorporates the Hebrew mindset expressed in "olam". In such cases, the translators would have served us better had they simply used the original word, "olam".
http://www.yashanet.com/studies/matstudy/mat3b.htm Greek or Hebrew New Testament.
http://aramaicnttruth.org/page.php?page=home Aramaic NT truth
This webpage includes ALL usages of olam in the OT http://www.seekfind.net/Bible_Dictionary__Define_olam_or_owlam__Definition_of_olam_or_owlam.html
Definition of olam or owlam: Long Duration
Strongs  says that this word can mean any of the following: long duration, antiquity, futurity, for ever, ever, everlasting, evermore, perpetual, old, ancient, world
By context, there is no place in the Bible that is in conflict with the definition: long duration. This translation may, at times, conflict with theologies but not with the Bible itself.
This webpage includes ALL usages of olam in the OT