For long term storage, it has always been susggested that every year or so you dump the water and refill it. Clearly, this is not because of the bottle; it might be to prevent overgrowth of the bugs that exist in small quantities in the water anyway.

I might be concerned about reusing those flimsy plastic bottles they sell in the grocery store, because they could easily develop cracks that might let contaminants in. But not the good quality ones like delivery water comes in -- which are reused anyway! Or the water drums sold for that purpose.

If you live in a place like LA, bottled water isn't a ripoff, it's a necessity. The tap water is disgusting. I long since gave up on tap water and bought a good water filteration system, which can be had for cheap than you think. You can take it with you and buy filter cartridges based on your need -- just look up your local water quality report. I can highly recommend these guys.