NBPRs and regular rebates are a great way to trick yourself in to save money. If you were going to spend $50 on groceries anyway and you can get a $15 rebate, just sock that $15 away in the bank or on a bill! It's free, found money.
Save those receipts when you purchase items at the store. You never can tell when a rebate is available :). It's free money, after all.