goodtimes
Expedition Poseur
Honestly, I think coffee will go south quicker than that. When I buy the good stuff (Stumptown), I notice a difference between the first pot and the last from the 12oz bag. I think that it starts to fade around a week out from opening the bag.
Yea, it can. It starts going south right away. By two weeks or so, it is completely flat -- and remember, that two weeks starts from the day it is roasted, not the day it was opened.
If it was packaged in the first day or two (while still outgassing CO2) in an air-tight container with a check valve (one-way valve), you have considerably longer because of the lower oxygen content of the container. Alternately, if it was flushed with nitrogen during the packaging process (after it stops outgassing), you achieve the same thing. Either one of these will give you a few months, possibly longer -- but once you open the container, you re-expose the coffee to oxygen, and you are back to your ~2 week window.
To add complexity, flavor is a bit subjective, and is related to the roast. Darker roasts lose some of the lighter flavors during the roast, so you can't lose those flavors due to oxidation -- they're already gone. So in theory (I've never tested this, so it is speculation on my part), darker roasts may last a bit longer than lighter roasts, before going south. Has anyone ever put "old" coffee side by side to compare how each roast survives? It would be interesting to see . . .