How long do they retain their qualities? In the coffee store near my home the seller told me that their coffee beans are stored for 1-3 months in their shop. But after purchase I'm also storing them for a few weeks.
I assume you are storing them for a later grinding (likely just before preparing your cups of coffee).
A brief summary:
For short term use (this week's coffee):
- Do not refrigerate your daily supply of coffee (in order to avoid moisture).
- Keep them in air-tight glass or ceramic containers, in a dark and cool place.
- Keep only the amount of beans you know you will quickly use.
For long term use (no more than a month):
- If you have a large amount of beans, wrap them in small (weekly) amounts inside air-tight bags, and freeze them. Once removed from freezer, do not return them.
- If you are making coffee in an espresso machine, let them getting room temperature for one day.
Coffee is fresh only for about 7 days from roast. I tried keeping in cool place, freeze and many more options but did not help too much, so I decided to get a coffee roast machine and just roast as much I need for the 1-2 days. All this is from my experience, not from books or anything else. If coffee is out for couple weeks or months than is not tasting and does not have potency as should have.
The problem with coffee beams is the same as with any other product that has open/direct contact with the environment:
- oxidation (contact with oxygen): covering all the aroma under a heavily bitter taste.
- humidity absorption: smell and taste circulating in the surrounding of the coffee will be imprinted in its taste as it will be diluted in the water vapours and absorbed from the beams. (This phenomena if especially important after the grounding, for example if the barista is smoking or heavily using deodorants etc, all of these will be imprinted in the coffee taste).
- loosing aroma through evaporation/drying (as temperature changes during the 24 day, during the hotter hours it will dry and the rest absorb).
That is why coffee companies make everything possible to pack and isolate the beans/ powder once baked. Illy for example insert nitrogen gas to prevent oxidation, etc.