It sounds like you've thought this out pretty well. I think you might be on to something.

The only reason I brought up purity concerns is because I have noticed a difference in stored bottled water as opposed to stored drinking water. I've drank 1-2 year old bottle water with absolutely no indication of old age, where as after a few months, regular drinking water stored in a Nalgene bottle starts to smell a little funny. I'm sure it's still drinkable, I just notice a smell, so I assume that there is probably somethign in the water. I admit that I don't go through the precautions when filling up the bottle, it's just a straight fill from the water cooler, so that could be the cause of it.