Opened on September 18, 2014, the initial aroma of the grounds seemed to match that of a fresh can. IMHO, the early taste and aroma of the brewed coffee was surprisingly acceptable. In the ten days since opening, the brewed coffee has no aroma to speak of and there now is a noticeable stale taste. But hey, during my lifetime I’ve had coffee that was much worse; if we were five years into an apocalypse, I’ll bet I could muster a few paying customers.
We’ll finish using up the contents of this can, but, short of TEOTWAWKI, I see no compelling reason for us to ever repeat this experience.
EDIT: I have been experimenting with nuking the grounds in the microwave (in a dish, not in a paper filter) for short lengths of time before brewing; it seems to blunt most of the stale flavor.
Below are some raw links on keeping coffee.