I don't say you are wrong, Leon, (I have no idea) but do you have any sources you could share with me to back that up? I'm a trust but verify kinda girl.
The reason I ask is, the pouches I looked at on Amazon were called Datex Emergency Water Pouches and they had an alleged shelf-life of five years. See
http://www.amazon.com/Datrex-Emerge...OW96/ref=sr_1_1?ie=UTF8&qid=1336308194&sr=8-1. Also, the Mormons say:
Water Pretreatment
Water from a chlorinated municipal water supply does not need further treatment when stored in clean, food-grade containers.
Non-chlorinated water should be treated with bleach. Add 1/8 of a teaspoon (8 drops) of liquid household chlorine bleach (5 to 6% sodium hypochlorite) for every gallon (4 liters) of water. Only household bleach without thickeners, scents, or additives should be used.
See http://www.providentliving.org/content/display/0,11666,7534-1-4065-1,00.html
However, they also say the water must be emptied and refilled regularly.
I admit to having trust issues w/the gov't sometimes and don't always believe everything they tell us, but I have no issue w/believing FEMA when they say:
Filling Water Containers
If the tap water has been commercially treated from a water utility with chlorine, you do not need to add anything else to the water to keep it clean. If the water you are using comes from a well or water source that is not treated with chlorine, add two drops of non-scented liquid household chlorine bleach to the water.Tightly close the container using the original cap. Be careful not to contaminate the cap by touching the inside of it with your finger. Place a date on the outside of the container so that you know when you filled it. Store in a cool, dark place.
However, they agree w/you that you should "Replace the water every six months if not using commercially bottled water." See
http://www.fema.gov/plan/prepare/water.shtm
I would think, however, that an argument could be made that if you had the water stored for a couple of years and then boiled, used Clorox, or otherwise treated the water before use, it would be at least as safe as what you might get from your local river, no?
Then again, it wouldn't really be that big of a deal to empty out the Mylar bags every six months, clean them well with a Clorox solution, and refill and reseal for another six months. Heck, I bet you could use those same bags for four or five years, although you would lose volume each time.