Quote Originally Posted by robert2008 View Post
Over time, dirt and dust can accumulate in car AC vents. If neglected, they would cause polluted air within your car and even mold growth, which emits a musty odor. That is why car vent cleaning must be regularly done once or twice a month or more if necessary.
I don't disagree that the fact that air vents could do this on neglected cars, but every 2-4 weeks seems excessive.