I am not much of a history buff. I am just a Bible guy. I used to believe in Eternal Conscious Torment (ECT) and I even defended it at one time. I then learned of the Conditional Immortality, and I was on the fence for a good while between ECT and CI (Conditional Immortality). Then one day when I started looking at more verses for Conditional Immortality from reading a really good article, I was convinced that it was true. What helped me to be convinced even more beyond this was the fact that Conditional Immortality is moral, just, and good (Whereas ECT attempts to turn God into some kind of monster), as well. For I believe every teaching or Godly truth in the Bible should always be good, just, and moral.
I believe in reading and using Modern Translations, but my final Word of authority is the KJV. So if the KJV says "forever" I believe that. But words from the 1600's don't always have the same meaning as they do today; And we have to sometimes think outside the box to see what God is really telling us, as well. This is why I believe the word "forever" is used in context of within something that is temporary, like a Covenant, or here upon this Earth (which is temporal), or within the Lake of Fire (Which is also a temporary place or form of punishment). It is "forever" for as long as that thing exists. For example: A husband might say to his wife that he will be her man forever. This is context to as long as they live (of course). Forever is in context as long as they live. It is a metaphorical expression. For are we to assume that Onesimus is still alive with his master today according to Philemon 1:15? Surely not. Onesimus return back to his master for "forever" was not for all eternity. The word "forever" in Philemon 1:15 is clearly in context to as long as Onesimus would live.
As for the English word "hell" in Matthew 10:28 taken from the Greek word "Gehenna" meaning the "Lake of Fire": While it is helpful to look to the Greek to get a clearer picture of what Matthew 10:28 is saying, I believe the "Lake of Fire" (Gehenna) can also be called "hell" (even though "hell" will be cast into the Lake of Fire). How so?
Well, "hell" is sort of like an island sitting atop of the Lake of Fire. The Earth's core is like a big fiery hot ball. The great gulf is an opening or crack in hell's surface letting some of the flame from below (in the Lake of Fire) to show (Whereby the Richman is tormented by the heat of it).
Deuteronomy 32:22 "For a fire is kindled in mine anger, and shall burn unto the lowest hell, and shall consume the earth with her increase, and set on fire the foundations of the mountains." In other words, the lowest "hell" is the Lake of Fire.
Isaiah 34:14 "The wild beasts of the desert shall also meet with the wild beasts of the island, and the satyr shall cry to his fellow; the screech owl also shall rest there, and find for herself a place of rest." And the wild beasts, the satyr, and the screech owl in this passage are demons. The wild beasts of the island are those demons on the island of "hell" below.