Let’s first specify where not to store: in the fridge or in a freezer. Doh!
Old Rock did the test itself. We stored 8 bags of the same coffee in the freezer. Every month, we brewed coffee with a new bag. The first bag was fine, then the second bag was slightly different but still good. By the third bag, we knew something was wrong. We had to throw away the fourth and remaining bags.
We did the same test with coffee stored in the cupboard. After 4 months, the coffee was still good.
The morale: store your coffee in an air tight container that was never used for anything except for coffee. Keep the container, preferably a glass container, in the lowest area of a cupboards that is against an inside wall of the house/apt, in the dark. This approach will ensure maintain optimum freshness for as long as possible.