MRC01, wherever did you hear that moisture causes microphones to deteriorate? Condensation of moisture in the capsule (i.e. actual water droplets forming) will interfere with the functioning of any condenser microphone. But once it evaporates, the microphone should be fine again, if it was any good to begin with.
So you don't need to take any special measures to avoid ordinary, non-condensing humidity in storage. Mainly what you need to avoid in storage is dust. And theft. OK, well--dust, theft and packs of marauding jackals. And angry men swinging pickaxes. For ribbon microphones, the list of things to avoid would include iron filings along with ordinary dust. But otherwise it's just the usual dust / theft / jackals / pickaxes.
Cardioids sometimes have special dietary restrictions. If your microphones are made of straw, teach them basic fire safety and don't use them to close-mike a vocalist who's been drinking kerosene, unless you're using an asbestos windscreen. Stuff like that--just common sense, really.
--best regards