What i'm trying to say is that while there is that tower in lavender town you don't actually see pokemon die in the anime or game
i mean sure charmander is said to die when the flame on it's tail goes out(it never does)
and not every pokemon has a flame on it's tail
they don't seem to have ages either
IKR? Although when I battle, I say they "die" when they faint XD
As evidenced by manga and in-game pokemon previously posted, pokemon die, either due to natural causes (sickness, old age) or not (avalanche, cruel death, etc)
However I think that they do not die in-game to (1. make it easier to make the game and (2. Create a sense that the trainers are capable enough to stop battling before their pokemon are dead.
I mean, why else would they use struggle when they have no "power" left, and why do we see their hp levels? I think that there are a lot of implied rules in the pokemon series regarding battle that are never really explained-but can cover the lack of pokemon dying in game.