Butter tastes great on just about anything: bread, vegetables, pasta, burgers, you name it. Clearly, you don't want to waste it. You can keep butter one to two days if out at room temperate, as the oils can spoil, or one to two months beyond a sell-by date if refrigerated. Plus, take note: salted butter will keep for longer, as the salt acts as a preservative, so for salted, it could be three or four months if left in the fridge.