I'm wondering about this topic for a while. As I know there is no official answer to this problem, and everywhere I look that main discussion seems to be looped on XX121 life cycle. I would like to see your opinions about it.
If we assume that alien organism is in fact artifically created bioweapon, it would be logical for it to have extremely short lifespan - maybe even days or weeks. It's life cycle also points towards shorter life expectancy - unusually fast growth rate means super fast metabolism and could mean that if XX121 grows so quickly, it gets older and die rather fast. We know that's the case with Neomorph - they grow old and die within days. I am aware that Ridley Scott said in one of the older interviews that it is exactly the case - in the ending scenes of Alien, XX121 on board of the Narcissus is so sluggish because it is already dying. It's color becomes more black, relative to grayish blue we see when the creature is young, pointing towards it's age. Of course we can also say that the alien just prepared itself to hibernation. However, one does not excludes the other. Creating deadly biomechanoid murder creature designed for urban pacification, who is at the same time extremely hard to kill, can suggest that it's wise to make sure it will die rather fast after completting it's work. Maybe hibernation in damp, warm places can extend lifespan into weeks, but we can still be sure that couple of months after initial egg bombardment the area is relatively secure (except the eggs themselves).
In Aliens this seems to be exactly like that, between lost communication with Hadley's Hope and arrival of Colonial Marines some time has passed. Yet when marines enter the Hive they encounter cocooned woman about to give birth to a chestburster. This may indicate that XX121 do not fertilise all their potential victims too fast, but instead keep them cocooned inside the Hive and only release facehuggers when there is need to it (ie. when population of the Drones start to dwindle). That means there is no Xenomorph homeworld and it's species is not result of natural evolution - from the beginnings to the very end, each moment of creature's life is designed with malignant purpose. IMO this only magnifies the nightmare of Alien milieu - think that Newt would survive in HH and just outlive entire Hive until the rescue arrives after whole population of XX121 just died. Instead CM came too early and it resulted in her untimely death.
One may ask - what with the Queen? I don't see a problem with that. The only subspiecies of the Xenomorph with longer lifespan should be Ovomorph. What can be more sweet than weapon that replicates itself for us? There is no reason to create the entire infrastructure, which would be designed to produce eggs for military purposes - all we need is a simple laboratory and our biohorror will create more eggs for us, either through Lurkers ovomorphing venom, or through fully developed Queen laying entire hatches of eggs.
Or maybe it's entirely different than that. Maybe drone can live for decades, there is Xenomorph homeworld, even entire worlds overrun by the XX121 species, giant Hives spanning whole continents and complicated social structures, sub-species of those horryfiyng creatures? What is your opinion and what is your canon?