If the beer's any good, it'll be drunk LONG before it goes "bad."
Remember, beer doesn't really go bad, per se, it's just gets a little... off. Hop flavor and bitterness drops out, they might get a bit of an oxidized character. Older wheat beers have kind of a weirdness to them (it seemed that my hefes get more and more banana-ey as time goes by). But, there's never a point at which the beer would make you sick if you drank it. It's not milk!