Pet food quantity - large package or small package?

I have found that the best value for me, and the best option for my dog, is purchasing a big 40lb bag of dry dog food. Since my dog eats about 3 times a day, he ends up finishing those 40lbs before the bag goes bad. And buying the big bag is cheaper than purchasing the same amount of food in smaller quantities. For example, I used to buy the smaller 8lb bags, but I noticed I would have to buy bags more often. Once I did the math, I found out purchasing the large bag is cheaper for me than purchasing the smaller bags. And that means less trips to the store. My dog is happy with a full stomach, and I am happy with a full wallet. Everyone wins!