I recently purchased a bag of dessicant from Bass Pro and split it up into tube socks for each of my ammo cans (it was pretty close to a 1lb bag of the stuff).  I know that you can recharge (ie dry out) the dessicant once it has become saturated in an oven, but how do you know when to do this and how often do you have to do it?  I usually open the cans once every few weeks to load ammo into mags and in such a small space I would assume that the amount of moisture in the air allowed into the cans is fairly low because its always in an AC environment.  So when do most of you replace your dessicant or recharge it?