But remember that the book of revelation is what John saw in a vision. Did John see smoke going up forever or did he see a lot of smoke? I think it is safe to say that this vision took place in a fairly short period of time and therefore it is not remotely possible that he literally saw the smoke going up forever and ever. Just one of many problems with the literal interpretation of that verse.
Elsewhere we are told that every man will be tried for what he has done by fire, gain reward or suffer loss but he himself shall be saved as by fire. We are told again in revelation that every man will be judged by what he has done. The lake of fire is said to torment those who are within, it is said to contain brimstone which was thought to be a purifing agent. The word torment means to test the purity of gold and silver, elsewhere we see that the fire tries our works be they gold and silver, hay and stubble, gain or loss but salvation regaurdless. We are told that it is Gods will that every man be saved, that no one can twart Gods will and that God is not willing that any should perish.
When we drop the literal understanding of a verse that is not literal the concept of eternal torture goes away with it and we see a much brighter light than ever before in that not only did God have a plan to save everyone but that he will do so.