“They will be punished with eternal destruction (olethron aionion)” (2 Thes. 1:9). Aionios means enduring through or pertaining to a period of time. Both the noun and the adjective are applied to limited periods. Thus the phrase eis ton aiona, habitually rendered forever, is often used of duration which is limited in the very nature of the case.
On the words often translated “eternity” and “eternal” in the Bible. From Thomas Allin’s Christ Triumphant.
“God’s purpose in creating man, and God’s purpose of the eons are inseparably related. Many are unfamiliar with this important subject because the facts have been concealed by incorrect and misleading translations of the Bible from the original languages into English.”–Joseph E. Kirk