My original question was concerning canister type filters in which the filter and canister are all one unit.And it is impossible to drain all the water out of them. Yes they are good for one year. but you can't let the old water just sit in them and think they are good to go a few months down the road and continue to use them until that year is up. I realize there are filters that you hook up on the end of your hose and yes they can be changed out rather cheaply. But canister types are 50 to 60 bucks a pop.And to buy a new one for a 2 week vacation is just ludicrous. So I think putting them in the freezer might be the answer. How many do that ?