Brown sugar does not spoil because it does not promote the growth of microbes; however, brown sugar that dries out becomes too hard to use for cooking and baking. Brown sugar consists of granulated sugar and molasses.
Properly stored brown sugar lasts indefinitely. Brown sugar is best stored in an air-tight container in a dry location. To prevent brown sugar from drying and becoming hard, keep it away from light and heat. Brown sugar should not be kept in the refrigerator though it can be frozen. The flavor of brown sugar is generally best within six months of purchasing the product.