I wonder about the life cycle of Engineers

good question, but who knows at this point? It would be a major plot spoiler.

my [url=http://www.prometheus-movie.com/community/forums/topic/4065]speculation[/url] is that they are long lived or undying.

some thing we have not seen yet or know about can`t wait

There are no living SJ on the planet you see the corpses when they enter the temple/lab.

that would be explained in Prometheus II The Return of the SJ.. lol

There is an SJ getting out of the chair. If you look closely he is getting out not getting in, so there is at least 1 SJ alive and kicking on the planet

I'm surprised that no one has commented on the fact that not only were the eggs a later zenomorphs a product of the SJ's but so too were the praetorians a product of them

[quote]that would be explained in Prometheus II The Return of the SJ.. lol[/quote] No....Prometheus II will be "The SJ Strike Back".... Prometheus III will be "Return of the Fleshy People".... : )