Simple syrup typically lasts about 2 weeks to 1 month in the refrigerator when stored in an airtight container. A standard simple syrup made with equal parts sugar and water usually keeps for around 2 weeks, while a richer syrup (2 parts sugar to 1 part water) can last up to 6 months refrigerated. Flavored or infused syrups tend to have shorter shelf lives, generally lasting 1 to 2 weeks depending on the ingredients added. Proper storage involves using a sterile, airtight container kept in the fridge to extend freshness. Signs that simple syrup has gone bad include cloudiness, off smells, or mold growth. Freezing simple syrup is also possible, which can preserve it for up to a year if stored properly.