Oh, and I'd personally be more worried about what affect the off-gassing from whatever chemical I used on the rubber might have on the brass than I would be concerned about whether or not I needed to store the ammo in an air-tight container. Ammonia and other chemicals are very, very bad for brass. That would worry me a lot more than the rubber on the can.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.