I think there are a LOT of people who do what you do. Every few weeks we have an 8 hour sale. Stuff is dirt cheap. We are SOOO busy on those days. Meat is a big one (88/lb for hamburger, 2.99/lb for nice steaks, etc)...cereal for $1 a box, bottled water is HUGE. I swear they bring out 100 pallets during the day.
Today is one of those days so I should be rather tired this evening. 
Abbey