These are called aged coffees. Once roasted, coffee beans are quite porous and susceptible to the absorption of moisture. Stale coffee beans thus become softer and grind differently than freshly roasted beans. If you know the altitude at which a coffee is grown you will have a good clue as to its flavor and acidity. As a general rule, the higher the altitude, the more delicate the flavor and crisper the acidity.
Coffee is a seasonal commodity.
When coffee is harvested and how often it is harvested determines the availability of the coffee beans. Sometimes the political climate in a country can also influence when beans hit the market. Estate coffees are generally quality Arabica coffees grown on an individual owner's farm and not mixed with coffees from other plantations. The best coffees are picked when the coffee cherries are ripe. However, in many cases, coffee cherries are picked too early or late.