So long as the cartridge is stored at room temperature, we haven’t had a lot of issues with leaking cartridges, even over long spans of time. The main cause of leakage is when a cartridge gets very hot (such as when it is left in a hot car, out in the sun, etc) and the oil gets very thin. If kept at room temperature (air conditioned room if we’re having a heat wave!) leakage should only occur in the rare instance that there is a defect. And if that is the case, we stand behind our products 100% and will always replace any malfunctioning device! Patient care is our #1 priority!