I used to argue for the proper understanding of the Greek eon and Hebrew olam, perhaps because understanding that freed me to believe UR. But, so many won't understand the difference between the original languages and a translation no matter how hard you try. Now I find it much more convenient to point out examples of how "forever, eternal, perpetual, and everlasting" are English words you cannot believe in the Bible because they are are applied to things that end after 3 days, a lifetime, 'til "the elements melt with a fervent heat, and the heaven disappear with a loud noise," and so on.
I really don't see that ET is on some kind of similar footing as UR in the Word. There are only about 2 or 3 references that can be construed to teach ET, but only if you don't take too close of a look at what is or is not said and what is in the original language. Here's an example which is not matched by anything ET offers: The angel that announced to the shepherds who were out with their flocks under the beautiful night sky, "I bring you glad tidings of great joy that shall be to all people!" Have we gotten it wrong all these years? Was this a holy angel or a demon? Should it have been said, "I bring you glad tidings of great joy that shall be to SOME, NOT all people!?"
Here's another from Jesus: "If the blind lead the blind they shall both fall in a ditch." I was taught to add: "And so they were for evermore." Really, they are there to learn they followed the wrong man and what the way out of the hole they're in."
On and on...Jesus telling us to tell the good news to every creature would mean He's intentionally making us liars since He already knows who is saved and who is damned. Only the worst possible news is true for the damned (under the ET doctrine.)
So many attributes of God are undermined if we were to believe ET.
It just goes on...many direct sayings of Scripture teach UR.
Mostly I find such expressions as in the OP to be made by those (who comprise about 96.5 % of "Christians") who have not and do not read the Scripture, but for a verse here and there. Seldom or never do they study something in Scripture. How to use concordances is not taught in almost all the churches. They depend on God placing over them as their source of what to believe their Pastors or Priests or Rabbis. Another point to make here is that those who interpret Scripture for most today, those determining what the mainstream orthodoxy is supposed to be, is something like a rock star. Their faces are all over the world through popular media. Millions look to their televangelist to tell them what to think and do as a Christian. Nobodys like us don't have any weight. We just are not "ordained" or some other such qualifying through Institutional Religion.
I'll tell you a secret...it's the nobodies who love their fellowmen, who are inebriated with the love of God and are walking in His ways, being made conformable unto the likeness of His death, who will be anointed with the Holy Ghost and power to make the nations obedient to the gospel.