Bottled water shelf life for emergency use is definitely longer than a year.
Water doesn’t “go bad” in a sealed container, at least from a bacteriological standpoint. There are some microbes in the bottle to begin with but they can’t multiply without energy. You may over time get more leaching of chemicals from the container, but that is only a concern if you would drink that kind of water for a long time. Of course, if the container is faulty or the water is of poor quality to begin with, the above doesn’t apply.
I don’t mean to say anything about safety with this anecdote (only about aesthetics), but I once drank 1.5 liters of at least 5 years old bottled water from a plastic bottle. Although it tasted a little bit of plastic, it was not unpleasant. In an emergency situation this would be just fine.
From the FDA (via Wayback machine):
Bottled water is considered to have an indefinite safety shelf life if it is produced in accordance with CGMP and quality standard regulations and is stored in an unopened, properly sealed container. Therefore, FDA does not require an expiration date for bottled water. However, long-term storage of bottled water may result in aesthetic defects, such as off-odor and taste. Bottlers may voluntarily put expiration dates on their labels.
I would say good quality, commercial water in a bottle lasts as long the bottle lasts. At least for survival purposes.
