The immortality is all based on accessible sunlight. A nuclear winter would knock years of his life span. Then again, who knows how long Kryptonians with out solar enhancemnt last, since that whole "stones" bullshit and veritas bullshit was set up by Joer-El hundeds of years ago but he visited the 50s as a teen ager, although that gemologist fromt he beginning of season season had been alive since cowboy times while being down powered by some special sort of Kryptonite, Blue maybe? MAGNIFICENT!!! Between Persuader and Doomsday, I do feel cheated b y the moritorium on costumes for the last 8 years. Something about lightning lad wanted to have me hit hm in the face.