Hi Agua,
I agree with your conclusion that the fate of the wicked is permanent destruction, but, I don't see how we can define "aionios" as eternal anywhere. I think if we do that we create a conflict with other passages of Scripture. Let me explain, if we say that in Mathew "aionios" (which is the adjective form of aion) means eternal and we say that "aionion" is a limited period of time that came to an end in Ex 28:42-43, we're essentially said the word means eternal and not eternal. If the word means eternal and not eternal how do we determine where it means eternal and where it doesn't mean eternal? You see I think this is how theology drives the interpretation. If it can mean eternal and not eternal then we can pick where we want to say it means eternal based on what we believe. If I believe in ECT then I can say that Rev 20:10 says the beast, the false prophet and the Devil will be tormented for eternity, however, if I believe in CI and translate it as a period of time and say that it will end. I believe that word "aion" is translated correctly as an age. I don't understand why the translators would change the meaning of the word simply because it's used as an adjective.
To address Mathew 25 specifically, I do think the punishment is eternal because it's contrasted with those going into the Kingdom and Scripture tells us that the kingdom will have no end. The phrase, "will have no end" means eternal. The life that is given to the believer is eternal, not because it's called aionios life, but rather because Jesus said that sons of the resurrection die no more.
35 "But those who are counted worthy to attain that age, and the resurrection from the dead, neither marry nor are given in marriage;
36 "nor can they die anymore, for they are equal to the angels and are sons of God, being sons of the resurrection.
(Luk 20:35-36 NKJ)
"Nor can they die anymore", that is eternal life.
It's a fine line that I'm trying to draw here but I think it is a very important one if we are going to grasp the Scriptures correctly. Let me reiterate that while I say I don't believe that "aionios" can rightly be defined as eternal that doesn't mean that an "aionios" time can't be eternal. Does that make sense? Aionios time is unspecified, as such it can refer to any period of time, it just isn't specified. If we define aionios as eternity then we have just given it a meaning of definite time, eternity. If it means eternity then it can't mean a month or a year or 10 years, it has to mean eternity. If that is the case then we have to do as the English translators have done and say that the ordinances in the Mosaic Law are eternal ordinances. If we do that then we must conclude that the Old Covenant is still in effect and will be for eternity. We must also conclude that Paul was mistaken when he said that the Mosaic Law had come to an end. Jesus said that He had come to complete the Law, one must conclude that this is not the case either.
I don't see any reason that aionios should be translated as eternal, it's not necessary to do so to show that believers have eternal life. And, by doing so they create a situation where an incorrect reading is read back into other passages. I believe this is the case with Rev 20:10. Since translators have defined aionios as eternal because it speaks of the age to come, the word eternal is then read back into verses like Rev 20:10 and then we have doctrines like ECT come into being because eternity is read back into aionios.
Does that make sense? It's a little difficult to explain it all in a post.