Let's first talk about timing. Most beans I see people using are dead on arrival. Whatever else they do right, they are using expired beans. This stems from a common misconception that coffee is a "dead" substance so-to-speak. It's quite alive in the sense of the chemical reactions happening immediately after roasting.

The curve (../core-concepts/the-curve) for roasted beans is about two to three weeks. Personally, I don't like anything older than two. Because a bag can last me about a week, I won't buy anything over about a week and a few days old.

Why a week and a few days? After roasting, coffee is not ready to drink. It needs about three days for gases to release and some oxidation to happen for optimal flavor. So the best bean to drink from is about 3-4 days roasted.

If you buy your beans from the grocery store it's almost entirely certain they are well past ../core-concepts/the-curve.

Second, beans should be ground per cup. Once ground, the oxidation proccess rapidly accelerates and will leave you with freshly roasted yet stale coffee grounds if not consumed the same day, maybe less than that even. See ../../grinding for more information.