You also need to think about the kind of food qe're talking about. Milk has a date after which the product my start to turn and curdle. Dried pasta has a date after which... the quality might suffer a little? Fruit goes mushy and baked goods mold. The dates put on these items are designed to limit liability of the company(s) providing them. You don't put 4 weeks on a bottle of milk thinking it will turn at 4 weeks and 1 day, you put 3 weeks on it knowing that it gives you leeway, not only for time, but also quality of storage. If you buy a bottle of milk but it takes a couple hours to get it back into refrigeration, of course it will affect the life span. And no one is talking about giving away bloated canned goods. Dented cans are most often sent back to the warehouse, especially if the dent is on a rim or seal.