I know some may say.... what about Sodom and Gomorrah? The scripture says that their fire will burn forever. So it couldn't really mean forever could it?
Well, I think that is evident that it does mean forever. The souls that were in Sodom and Gomorrah are still in hell awaiting judgment, and when judgment comes they will be thrown in the Lake of Fire forever. So yeah, God set them on fire, they are still burning, and will burn forever.
Jude 1:7
Even as Sodom and Gomorrha, and the cities about them in like manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire.
So yeah, It seems their fire will burn forever and never be extinguished.