I have had some coffee beans for over a year now and the date on them is July 2015. I have been drinking them for the past year because I have a big supply. The coffee still tastes great and I can tell the caffeine still has an effect on me.
Is this bad? I'm storing them at room temperature and I grind and drink the coffee on the same day.
Normally, the main reason that roasted coffee has a shelf life is its freshness. If the package is properly closed it is mostly safe. Your concern should be its flavor which should be faded away already.
However, you must also think about the mold that may cover the beans. Mold may grow on coffee beans or ground coffee in time. It may cause allergic reactions according to this site or even more. This site includes a guide how to remove mold from coffee beans -however this method affects the flavor.
Maybe a physician could be more helpful about the health effects of mold.
In the retail world, "sell by date" is very different from "date of expiration". With that said. Coffee is a fruit. It is perishable, even after it is roasted and can grow mold. Additionally, if you are using a standard brewer, the brewer itself can be susceptible to mold caused by water condensing inside the machine. Unless the coffee has been stored improperly until today (stored in a moist environment with light, exposure to elements, etc.) I would think it would be okay to drink. Coffee is all about taste; to another person, old coffee will taste flat and not have such an aromatic flavor as freshly ground coffee.
If there is visible mold on the coffee, I would not drink/grind it. The best thing to do is always consult your doctor before doing anything.
