I hike a lot, and left canteens for up to a month with water in them. My preferred water containers are Powerade bottles, they are just the right height and width, and I prefer a clear water bottle over one you can't see through, since I filter my water through a t-shirt and use Aquamira drops, one look and I can see if any floaties got past the tshirt.

 
 
The two most abundant elements in the universe are Hydrogen and stupidity.