I use the concentrate Sta-Flo, 50/50 and haven't had any problems with it "going bad" after sitting in the spray bottle for weeks. I starch my fabrics that I'm going to be using a minimum of 2 hours BEFORE I'm going to use it, then dry it. I also have had the starched fabrics in the plastic bag for 2-3 days and haven't had a problem. If it was going to be longer than that, I would put the fabric in the freezer, then take out when you're ready to use them. As far as the "bugs" such as silverfish, etc., if you don't have a problem with them previously, I don't think you'll have a problem with them now, just because you're using starch. We don't have a problem with them and it hasn't changed because of the starch.