If what you're concerned about is deterioration of the plastic, we explored that a bit with regard to water containers in the PSK. Once upon a time (11/01) we did the "Great Water Container Test"
http://www.equipped.org/ubbthreads/showt...;sb=&o=Basically, with twice the normal concentration of Potable Aqua, and NO attempt at aiding dissolution of the tablets (I just dropped them in, so they mostly sat in one spot slowly dissolving), there was no apparent deterioration of any of the containers in two weeks. The only container that failed in the first month was the latex condom, and that lasted almost a month, faling sometime in the last two days. At two months, the latex balloon had lost a lot of water somehow, but was still intact. The zipper lock bags had also lost a lot of water (evaporation, I think), but were also fine. All the other containers (fish bags, oven bags) were still full and intact. There was no visible effect at all on the polyethylene containers, only the latex.
Considering that the hydration bladders are a MANY times thicker than any of the containers in the test, I wouldn't worry about that aspect. They will stain, but that's it.
Nalgene bottles have been used for long enough that I would really be shocked if they were affected at all, either.