Salesguy, I have the same issue. My solution, so far, is the deluxe version of the General Ecology hand pump "purifiers". GE told me, in a telephone conversation, that the filters(unused) have an indefinite shelf life. I did not independently corroborate this advice. I also use the Katadyn "purifier" bottles with the Virustat a addition, for lightweight kits. Finally, in the ultralight category, I use the straw "purifier" sold by BQ and others.