An unopened dried dog food bag can last 18 months after production. But, after you open it, you should try to use it in the next 6 weeks. For maintaining freshness, keep the lid closed. Wet food, however, can last up to 2 years. But, it will quickly go bad if it stays too long inside the container. Even if you store it in the fridge, you will be using it in the next day or two. When either dried or wet dog food goes bad, they will develop a bad smell. The longer it stays, the bigger the odds of it showing signs of insects and mould build-up. To feed your dog fresh dry food, we suggest you buy smaller bags instead of purchasing one giant bag.