Wax is supposed to do two things: Give the paint job a shine and protect the paint from road salts, weather, etc. Unprotected paint oxidizes, meaning it rusts leaving a thin whitish coat which dulls the finish. If you have clear coats on top of the paint that process does not take place. Wax does not evaporate, does not just go away. It can over time build up and become something nasty on your car. 3 weeks to once monthly is the most you should wax your car if that much. It depends on how much your car is outside, what kind of climate/weather you have and what kind of clear coat you have. http://www.properautocare.com/whywaxyourcar.html makes for an interesting read. Modern Cars have a clear coat that is specially formulated to seal the paint against weather and UV light in essence they are wax-less paint jobs - meaning they do not need wax. Older vehicles (mid 1990s and earlier) do not have that coating and should be waxed. The newest technological advancement in clear coat finishes is a fluorine-type clear coat that needs little or no waxing. The most you need to apply "wax" (then its not really wax the owner's manual will specify the product one uses to maintain the finish) is 4 times a year if your vehicle sits out side and is exposed to weathering and UV light all the time.