We hate to waste food. I try very hard to use things up. We have never gotten sick on anything that has been in the frig a few days - like leftovers. I don't usually stock up since I am retired and can get to the grocery on my way to or from - I leave the house most days whether to go to the gym, my one morning a week part time job, or just because. From what I understand, the sell by date doesn't mean it will go bad. It helps stores rotate their stock.
Here is just one article I found on Mr. Google.
http://healthland.time.com/2013/09/1...ck-to-toss-it/