#203 - AN ANALYTICAL STUDY OF WORDS – Louis Abbotthttp://www.tentmaker.org/books/asw/index.html
Regarding the words translated "forever and ever."
"There are several analogous expressions in the Scriptures which should show the meaning of the words under discussion. In Ex. 26:33 (LXX), tou hagiou ton hagion, "in the holy of the holies." This is similar to the "eon of the eons" of Eph. 3:21. In IKings 8:6 (LXX) we see, eis ta hagia ton hagion, for "the holies of the holies" - similar to "eons of the eons." The "holy of the holies" and "holies of the holies" refer to the tabernacle. Psalm 44:7 says, ho thronos sou ho theos, eis ton aiona tou aionos, "Thy throne, O God, is for the eon of eon"-similar to Heb. 1:8. Daniel 7:18: "until eon of the eons" and similar to that of Eph. 3:21, where a singular is followed by a plural, "eon of the eons." In these expressions we see the eons corresponding to the holies in the tabernacle.
While there are many different teachings on the types in the Tabernacle of Moses, it should not be too difficult to see that there were at least five divisions: (1) without the camp; (2) in the camp; (3) in the court; (4) in the holy place; and (5) in the holy of holies. These may be likened to the five eons we find in the Scriptures (past eons, present eon, future eons). The last eon is called the "eon of the eons," because it, like the "holy of holies," is the climax of the others. In Hebrews chapter 9, the Greek text of Nestle reads (margin v. 25), eis ta hagia ton hagion, "into the holies of the holies," and (v. 3), hagia hagion, "holies of holies." Just as the two holy places in the tabernacle are called the holies of holies, so the last two eons are often called the eons of the eons.
As the tabernacle illustrated man's approach to God, it corresponds closely with the eonian times, which also brings man to God. The "holy of holies" was a single holy place. The "eon of eons," a single eon. It was the pre-eminence of the "holy of holies," in relation to the other holy places, which caused it to be so designated. So the pre-eminence of the "eon of the eons" lies in its being the fruitage and harvest of previous eons. The same is true of the "holies of the holies" of Heb. 9:25. They may be likened to the "eons of the eons" of Rev. 11:15; 22:5."