You keep your identity intact, if you die, your role in the RPG is over untill the next one begins.
As far as life span of both aliens and predators is concerned, there is still no hardcore evidence of them being able to live for centuries as i have read on many other websites.
Rference to a behind the scenes interview with Veronica Cartwright (Lambert from alien) She stated that the aliens only have very short life spans - hence the reason they change colours from a 'skin' like hue, to a dark black/blue - it was said that the alien is 'bruising' thus the urgency of the creatures trying to capture hosts for re-population before they die out.
Although this was discussed by Veronica, the theory is slightly unstable, as the warrior aliens on Acheron were nearly four weeks old at the time, Early specualtion stated that the aliens only lived a few days. But information differes from place to place so it's hard to pin point an actual truth.
www.thorndesigns.netdarkness of acheronBugRenders