I buy locally because it lasts more than a day. I recently bought a fresh head of lettuce and ate some of it 7 days after I bought it. It was still crisp.
When I buy produce at the store, I figure I need to eat it within 48 hours.
We buy a lot of our produce and meats either at Whole Foods or at the weekly farmers' markets in the DC area. A lot of times, the produce still has dirt on it, it was picked so recently. Compared to the produce you find at the major supermaket chains, which probably spent the last few days on a truck from California, it's like night and day.
There wasa great King of the Hill episode where Hank joins a co-op supermarket because he wants to be able to buy fresh, tasty produce and meat.