If you want to take this seriously you should be rotating all canned goods every few years. You're basically trading off the tiny cost of canned goods with a small risk of getting a disease from bad food (well-stored cans should be fine for 5 years, any bulging cans should be discarded), which isn't normally a huge problem, but during emergencies, could be.

If you look at history, a lot of wars were won or lost based on how well a city prepared for a sustained siege.

in the case of hiroshima, water pumps were restored 4 days after the bombing, but of course the story is more involved (http://www.hiroshimapeacemedia.jp/?p=47988)