Do the chemicals in the MICROPUR MP1 stop working after their expiration date? My package says it expired 01/2019 and I bought it less than four years ago- they don’t tell you the expiration date when buying online. Could somebody also say something about using bleach since I’ve read that bleach “expires” after about six months. Do they mean opened versus unopened and will it still be worth using after expiration date if nothing else should be available? Thanks