There have been quite a few theories about Xenomorph hives, lifespan and life cycle... It has been speculated that a Queen can live for thousands of years, Preatorians are young Queens, the nest is dried up slime (that same stuff that comes out of there mouth), the dominat Drones replace the dead Queen (This seems to be the case in AVP, as we Six see replaced the Matriarch), the Matriarch herself is an older Queen and Crushers and Preatorians are simply older aliens in the latter's case a warrior and the former's a Runner.
Others speculate that Boilers are extremly old or even possibly natrual Xenos, Queen Facehuggers if given the chance can impregnate more than two hosts, it has also been suggested that there are no male Xenos as all the reprodution is handled by Facehuggers and their hirearchy is similer to Bees/Ants/Termites and it's still open speculation as to how the Xenos came to be.
Personaly I think that Preatorians/Crushers are older Xenos.
Queens can live to see their thousands.
They have to make the hive somehow don't they?
The thing about Xenos is that they have plenty of ways to replace lost Queens.
The Matriarch is an older Queen.
Boilers are just mutants.
QF can impregnate more than two.
As for males... well Ridley said "It could just as easily be male or female".
I think the SJs created the Xenos as shock troopers to battle that 'unamed foe'.
These are just my opinions but what do you guys think?