I'm not up on my eldar fluff; what do we know of their reproduction cycle?

Eldargal, what do you imagine a craftworld's strategic commitments to look like? We're told that guardians are deployed because of a dearth of available aspect warriors, right? And we know that guardians are deployed on a regular basis, right? (Those are honest questions.) Let's assume that a craftworlder maintains a standing 1% of its population as active military professionals. If a craftworld has a billion eldar, that gives us ten million aspect warriors - even assuming as many as 75% of those are fleet personnel, that is about a fourth the size of the Vraks siege army - in aspect warriors. How many campaigns is a major craftworld involved in at any one time, that ten million aspect warriors or more is inadequate?