My wife worked part time as a "merchandiser" for Nabisco for a while. The job was essentially stocking all Nabisco product on the shelves. One of the responsibilities was removing outdated stock. Her co-workers seemed to do a pretty good job, she said she never found anything more than a week or so out of date. I wouldn't be surprised to find that to be true for other products stocked by the vendor, which includes a lot of dry products, and many beverages, including soda, beer, and dairy.

In places with high turnover, like Walmarts, she almost never found outdated stock. OT, but at Walmarts she also found a lot of packaging for CDs, DVDs, and other expensive items (contents removed) behind the stock.

OTOH, items stocked by the store personnel might not be so carefully monitored. My understanding is that would include most canned goods, items where there are only a few products from a specific vendor, and store brands.