I don't know about 2-3 years. I store my water in reused 1-gallon plastic water bottles. After thoroughly cleaning and disinfecting the bottles with dish soap and bleach, I rinse them well then fill with water. Then I add 8 drops of unscented bleach in just before tightly sealing. I store 28 gallons total (22 on the shelf in my downstairs pantry, 6 on the bottom shelf of the freezer), which is enough for 3 people to drink 1/2 gallon a day for two weeks, with an extra 1/2 gallon per day for cooking. I replace this once a year.

There's another 50 gallons in the water heater and whatever is in the pipes themselves. Just have to remember to shut-off the main supply to avoid contamination.