Why do grocery store and restaurant coupons expire? How would it hurt if they didn't?

In short: Inflation. Say a kid collects over 10,000 coupons in the 1940s and 50s and takes them out of the time capsule this year, by the time he or she is a grandparent. They then go on a shopping spree (and maybe give it to their sons and daughters to use them all faster). If these stores haven't gone out of business already, it'll take away from the profits because these stores will be forced to sell their products at the coupons' prices. Many stores and restaurants are afraid that customers will collect and time-capsule their coupons and sometime down the line, use them to buy what the coupons are for at deep discounts unhealthy for business. This is one of the reasons why coupons have expiration dates. ... more