There is absolutely no such thing as too clean! When I'm at home for Summer and Winter break, at the very minimum I wash my car once a week. Most of the time I will wash, and vacuum the interior, wax every month, and do a full detail every few months. Unfortunately at school my car sits outside in a gravel lot in the alley behind my house where dirt gets kicked up when people drive by. It stays clean for about a day before it gets a thin layer of dust on it, and about 3 days before it looks filthy again. I try to wash it maybe once a month (more often when the weather is nice), and detail it once every trimester. I can't wait to get out of Savannah in June so I can feel like my car is safe again, and clean.