Revival,
Your argument ignores the fact that eonian isn’t always used in ways that could even possibly mean “everlasting”, including in one of your own chosen scriptures (although you neglected to supply the preceding verse where no one of any belief for or against anything anywhere thinks the term means “everlasting”.)
Had you bothered to read or at least pay attention to the many other threads on this site (not to say elsewhere) discussing this topic, you would have known this already, and rephrased your argument to account for that.
Until then, no one here who has bothered to read on the topic is going to be impressed with a complaint wondering why 
URs merely “change” the meaning of eonian.
Thus your argument can be turned around:
“The ECT has no problem with interpreting “aionion” to mean something other than everlasting or eternal in Rom 16:25, but when the exact same word is used to describe God, the life of God, His power and life, suddenly ‘aionian’ means everlasting or eternal meaning. There are many more examples in the Greek Bible where ECTs treat eonian as referring to things that are and were not everlasting (even in cases where the original context might have been reasonably expected to mean everlasting), but Rom 16:25 will suffice. Why do ECTs think it’s Ok to do this? Why does not ‘aionion’ carry the same meaning in describing times previous to the coming of Christ, or hills, or the sacrifices offered in the temple, or the right of various families to do this or that, or how long Jonah was in the whale, as it does when describing the one and only unique God Most High and His properties? Everlasting is everlasting whether it’s describing God, the life of God, or things created or promised by God. The ECTs are not justified in picking and choosing the meaning of a word based upon their interpretations of ‘aion’ that suits them and depending on which verse is used.”
Any ECT with any experience at all would immediately and correctly disregard this argument, and would reply something to the effect of, “Duh, we interpret eonian according to the narrative and thematic contexts and/or according to previously established metaphysical positions, which is why we sometimes translate eonian as meaning never-ending, especially in regard to God Himself, and sometimes as meaning something that ends; and that’s also why we even do so on the couple of occasions, Rom 16:25-26 being one of them, where eonian is used twice in the same exact sentence with superficially similar but ultimately quite different meanings. It is therefore foolish for a UR to use our agreement that eonian doesn’t always mean everlasting as evidence merely in itself that eonian doesn’t mean everlasting when talking about punishment. Nor are we merely changing the meaning of the term around to suit our convenience in order to keep ECT going.”
Had you actually done more research on the forum, you’d already be familiar with arguments (including from myself) indicating that the context of 2 Thess 1:9 and of Matt 25 indicates “eonian” doesn’t mean never-ending in regard to the punishments.
My (and other) arguments might be wrong, but wrong arguments are not the same as merely picking and choosing the meaning of the word based upon the interpretation of “aion” that suits them and depending on which verse is used.
To this I can add (and have added in those arguments you couldn’t be bothered to even research before accusing URs of having no arguments at all but only convenient assertions on this topic), that non-universalists as non-universalists are absolutely committed to interpreting identical terms in close topical context in ultimately different ways, when dealing with scriptures where interpreting those terms identically would otherwise lead to a scriptural testimony of universal reconciliation of sinners by God. (One of those examples involves the term “reconcile” itself, at Col 1.) But those arguments are available in other threads, and you should already be familiar with how ECTs deal with such incidents anyway. If not, you’re welcome to go study them, and come back to try again when you’ve caught up enough to rephrase your challenge to something that isn’t a straw man of your opponents.
