Homemade simple syrup lasts about 1 month when made with a 1:1 sugar-to-water ratio and stored properly in the refrigerator in an airtight container. Rich simple syrup (2:1 sugar to water) can last up to 6 months in the fridge. Infused simple syrups with herbs, spices, or fruit have a shorter shelf life of around 1 to 3 months or even just 1 to 2 weeks if fresh ingredients like juices or purees are included. Room temperature storage reduces the shelf life drastically, causing spoilage in as little as one week. Signs that syrup has gone bad include crystallization, cloudiness, or an off smell, and it should then be discarded.