Always try to use any opened food as soon as you can
An opened bag of unsealed dry food has a very short shelf life – less than two weeks, and that’s a maximum. This is why you should be careful with how you open the bag to avoid tearing in a way that makes it impossible to reseal.
But even if you can successfully reseal the opened bag, the food inside is still perishable. Plus, Heinze writes, over time, the food will experience a process called nutrient degradation, which basically means the food is losing those benefits that make it a healthy choice in the first place.
Heinze told INSIDER, “It’s best not to buy more dry food than you can use in about a month or two.”
It can be a good idea to write down when you opened a particular bag to keep track since the expiration date usually applies to the bag when it’s sealed.