I test almost daily for FC, but I find the R-0870 powder doesn't keep well. I'm thinking of buying a 16 oz. size and refilling the kit as needed. Is that worth it, or will it go bad? I try to be careful with moisture, but I guess I'm not careful enough. Also, how do you keep the scoop clean? It gets all gunked up. Do you wash it and dry it well before putting it back in the kit? Any suggestions for keeping the moisture out? I've read a few posts about using one of those silicone pouches taped to the lid, doing the test indoors (away from humidity), etc. What works, and most importantly, should I buy the 16 oz. size?