I would recommend not trying to store water for longer than a month. Even if you treat the water with chlorine or iodine, it will begin to deteriorate almost immediately. I mark each container with the date and rotate the stores periodically. I figure on two gallons per person per day, and keep two weeks worth of water on hand.

If I haven't figured out another source of water after fourteen days, I'm in real trouble.

Onward and upward,
airforce