Properly stored, they last one heck of a long time. I keep mine in a closet that rarely if ever gets above 70 degrees F. I have eaten 10 year old main entrees and they were edible and not as bad as you might think. I gave a couple of packs of 10 year old crackers to my Mother-In-Law (no, it was not an attempt to do away with her) - She thought they were excellent and said if I was ever going to toss out the old ones she would gladly take them.
Lastly, if they get so old that you don't like them, my guess is that they will make a well appreciated supply of reserve Pet food.