On average, a reed diffuser should last 8 – 12 weeks, but this will depend on many factors, including the fragrance, type and number of reeds used, the position of the diffuser in the home and seasonal temperature variations. You will find that diffusion slows down in more relaxed environments and increases with ambient temperatures in summer. It can also vary in each room depending on air circulation. If your diffuser is diffusing too quickly, reduce the number of reeds in the vessel.