The sugar free chocolate one is made from cornstarch, cocoa, modified cornstarch and salt plus a bit of sweetener. That box is going to last for years. My husband had diabetes, so I didn't have trouble with rotating it. He ate it a lot.
I have the sugar one also and it has the same ingredients except it has skim milk, sugar and hydrogenated vegetable oil. According to the info. I got, the bit of vegetable oil helps preserve the skim milk.
So the answer is, I didn't note the date I bought them and I'm not concerned they would go bad. It's so easy to fix, eat them now for a sweet treat and buy more to replace those. If you need to control sugar intake, use the sugar free.