I noticed that on MoreBeer.com Gypsum, Epsom Salt, and Calcium Carbonate, are marked "perishable." What kind of shelf life do these brew salts have?
I've got mine in those cheap, disposable plastic Rubbermaid containers. Probably not airtight. I keep them on the shelf in the basement. Is there something else I should be doing with them? I know they're cheap, but I want them to last.