Beer is pasteurized or else full of live yeast cultures. It doesn't go "bad" per se in the sense that it will hurt you, but some beers taste bad beyond a certain point. Hoppy beers lose flavor in ~90 days or so after bottling. Mass-market beers "skunk" if they are exposed to light and the UV causes certain compounds to break down. Strong unpasteurized malty beers like porters and stouts can age for literally years in a cool dark place, and it smooths the flavors out.
> Strong unpasteurized malty beers like porters and stouts can age for literally years in a cool dark place, and it smooths the flavors out.
Had a coworker who made this phenomenon into a yearly gathering. We would bring beers of our choice, bury them in his back yard, then drink and grill/smoke meats. Next year he would dig up the previous years burial and we would try to bring the same beers with us. Then we all gather around and have a tasting comparing the year long aged beer to the fresh beer. You also brought along new beers to bury. He names it Man Beer Meat because it was just guys drinking and grilling.
That sounds like a wonderful time. And amusingly, if he moves, the new owner may do some digging in their backyard and find a bunch of perfectly fine bottles of beer.
