I think Pokemon age would roughly variate in accordance to the actual real life Pokemon they were based on - for example Wartortle, which is basically a tortoise which live for really long times, also does that.
Also they seem vary on random factors by gamfreak like Ninetale's;
>It can live for 1,000 years, due to the energy within its nine tails, each of which is said to have a different mystical power.
Absol;
>It is a long-lived Pokémon that has a life-span of 100 years.
Lucario did live for like a couple hundred years in Lucario and the Mystery of Mew but he was trapped in a staff and had no concept of time so I don't know about that one :I
Manmade Pokemon like Golett also are said to 'operate' for thousands of years
>A Pokemon that was made from clay using ancient scientific power. It’s continued to function for thousands of years.
We know Puka (Pikachu from the anime) was at least 20 years old, but nothing else :I
Logically speaking I would guess Ghost types live forever as do legendaries (I've seen people on other forums who are of a similar opinion like Serebii ;3), since Ghosts are well. Ghosts. And Legendaries are basically one-of-a-kind and control forces of nature and stuff like that. Though Latios/Latias are shown to have bred in Pokemon4Ever after Latios died and another 2 appeared at the end of the movie.
Anyway, I can't really give much of an answer but it seems that there is generally no link between each Pokemon's life expectancy. Well, most of them don't have anything about their life expectancy anyway. Pokémon was more targeted as a kid's game, so they obviously wouldn't introduce a mechanic where Pokemon died, or show Pokemon dieing in an anime. They might occasionally refer to it to add to the story (like Lavender tower), but in the end they probably threw it out to window for the benefit of the little kids who would go crying if their precious Pokemon died >.>
