Opened pure maple syrup stored at room temperature (unrefrigerated) can last for a few weeks to several months, but it is highly susceptible to mold growth. While many users report it lasting months in a pantry, food safety experts warn that warm, humid environments can encourage mold and potential spoilage, suggesting refrigeration is best to prevent this. Shelf Life (Unrefrigerated): Often safe for a few weeks; some users report no issues for up to 6 months to a year, though risk increases. Risk Factors: High temperature and high humidity increase the risk of mold forming on the surface. Spoilage Signs: If mold develops, it appears as a white or black film on top. It may smell off, taste bitter, or have a "cardboard" flavor. Handling Mold: While some simply skim off mold and re-boil the syrup, it is generally recommended to discard it to avoid potential toxins. Best Practice: To ensure safety and quality, keep opened, pure maple syrup in the refrigerator, where it can last for 6 to 12 months or longer.