At Gunsite they warned us as little as one summer in the trunk of a police car that stayed parked outdoors most of the time could kill primers so they didn't fire. The military intentionally heats powder to 140°F
to accelerate break-down to study the effect of stabilizers. Heat and shooting supplies are a recipe for encouraging future duds.
If you want to dry and store primers, get some freezer bags and a sealer and pack them in there with a desiccant pack. The mil spec ones are a smectite mineral clay like bentonite or montmorillonite and are available in tubs, like these
. Also, the Moltan oil absorbent granules
sold at AutoZone are pure montmorillonite clay, and you can spread them out on a cookie sheet and heat them in an electric oven at 250°F or higher to drive the water out. You are finished when they stop losing weight. Drop them into a cloth bag and pack them in the sealed bag with the primers.