The longevity of a reed diffuser depends on several factors, including the type of essential oil used, the size of the diffuser, the number of reeds, and the room’s temperature and airflow. Typically, a 100ml bottle of essential oil reed diffuser can last anywhere from 1 to 3 months. If you use more reeds or place the diffuser in a well-ventilated or warm room, the oil may evaporate faster. Conversely, using fewer reeds and placing the diffuser in a cooler area may help it last longer. To extend the life of your reed diffuser, avoid placing it in direct sunlight or near heat sources, and flip the reeds less frequently if you prefer a subtle fragrance.