According to the Alcohol and Tobacco Tax and Trade Bureau, rum has an indefinite shelf life as long as it is stored properly. Once opened, however, rum will only stay fresh for about a year. This is because rum is a distilled spirit made from fermented sugarcane juice or molasses, and over time these sugars will begin to break down and oxidize. So if you're looking to enjoy that bottle of Malibu rum you've had sitting in your liquor cabinet for a while, make sure it's been properly stored (i.e., in a cool, dark place) and check the bottle for any signs of spoilage before using it.