The shelf life of bleach is just 6-12 months. Because of this, I bought one pound of calcium hypochlorite from a pool supply company. This stuff has to be stored very carefully, e.g. NOT in its original plastic bag and not in a metal container or a container with a metal lid. It is dangerous stuff because it is so reactive. But its shelf life varies from 2 years on up, depending on whom you believe. Mixed in very small quantities with water, it will provide a disinfectant, not just for purifying water but for other needs, such as cleaning up after a sewage backup, which is entirely possible if electric power is out for an extended period. Do others have experience using or storing Ca(ClO)2? Does ThePrepared recommend this product? Safe storage is the primary issue.