Is it wasteful to buy three boxes of cereal when you need only one for a week? No, not if cereal is on sale. Over the long run it makes sense to stockpile enough groceries to last your family 10 to 12 weeks. Stockpiling allows you to take advantage of great sales and buy what you need before you need it, with or without using a coupon. Pay special attention to the expensive items on your list, and grab the opportunity to get them at rock-bottom prices when your store puts them on special. Of course, you should buy milk and fresh produce each week.