Generally water in the 1 gal jugs last 1 or 2 years before they develop a small leak somewhere. The jug that I use at work for a x-ray phantom has been replaced 3 times in 3 & a half years. They just don't last. There was another post regarding the same thing, water leaked out into a container and ruined batteries, etc. I went to buying cases of 12 oz. water on sale and replaceing them every 2 years . And we have the 55 Gal. drums.
Dave