I can go a couple months before I wash my car. It's just a Honda Accord. I do wash it if it's really dirty like after a snow storm. I want to get the salt off of it. Or if I went through mud or something. I'm perfectly fine with the rain washing it clean. haha
My husband washes his Impala SS like once a month or every other month! (SS stands for super sport and his car is electric blue) Yeah, it's that special! Boys and their cars!