Is Hell Eternal?

Something I've thought about for a long time, but haven't shared (because I don't like millstones around my neck), and was reminded of today with a Facebook post (which prompted my last post) is about time, God, Hell, and the release of spirits.  If time is not linear, God lives outside time, Hell is eternal, and Jesus preached to the spirits imprisoned in Hell, time is relative and can be warped, is it possible that every soul that will ever go to hell is already there, was there before The Crucifixion?  This seems to answer the paradox of what happens to those who die after the resurrection who knew not Jesus.  The spirits who accepted Jesus were released.