The OP asked about leaving his car dirty for a few weeks.Not for months or years on end. Vinyl and rubber trim that has been properly treated will suffer little from remaining dirty for a short period of time.Light dirt on a properly waxed or protected car will not acquire major paint defects in the rain compared to a improper wash. The largest contributor to paint defects is the improper wash and people dragging a microfiber across the surface to dust it off. I'm as OCD when it comes to detailing as most but a little common sense goes a long way. I have clients all the time that I have had to instruct that if you can't do a proper wash please leave it alone until I can service it. right now my work truck needs a wash ans it has been OC'ed but it will remain in need until this weekend when I have the time to do it properly. It has my detailing company logo on it but I won't compromise for a quick fix.