We appreciate you reaching out and sharing your comments! Whether the dial is at highest or lowest, the scent should last up to 40 days, depending on the speed and temperature of the vent. Other factors that can affect how long it lasts include how high and how often the heat or air conditioning is running. If the AC or Heat is on high, it may NOT last for 40 days. For maximum results of 40 days please keep it on low or medium. The product is completely used up when there is no longer visible liquid in the device, and the scent is no longer noticeable. We hope this helps, but if you'd like more information or having any questions or concerns, give us a call at 800-308-3279

We're sad to hear this. If you'd like to share more of your experience with us, we invite you to give our team a call at (800) 308-3279.