We are very sorry you’re unhappy with the strength of these. At the top of the clip there is an adjuster which lets you control the strength of fragrance. Whether the dial is at highest or lowest, the scent should last up to 30 days, depending on the speed and temperature of the vent. If on the lowest setting, it may last longer than 30 days. When you cannot smell the scent anymore, it's time to replace the clip. We always take consumer feedback into account when making changes or designing future products, so we'll be sure to share your comments on this with the rest of our team.