I keep reading all these posts about people having to get a new vapor canister because it got saturated and doesn't work any more. Corey was correct above - as long as the valves are working properly, the system will suck that gas back out of the charcoal and into the intake manifold.
Years ago I used to work on mass spectrometers. To achieve the ultra high vacuum needed to work properly, you have to get all the moisture out of the air, and the way to do that is with an activated charcoal cryogenic trap. You fill some loops of stainless steel tubing with charcoal granules and immerse it in liquid nitrogen. When you pass the sample stream through it all the water vapor gets trapped in the charcoal. When the charcoal becomes saturated, you just let it warm up to room ambient temperature and suck the water vapor out with a vacuum pump, just like the manifold vacuum does in a vehicle.