I used to have this silver colored 2003 Mercedes C320 that I never washed. I have had some work done on the car and the repair shop washed it, but I never did. I just let the rain do it for me.
Nine years later, after about 79,000 miles I gave that car to a friend who just graduated from high school. But right before I gave it away, I washed it and the paint job was gorgeous.
This is what she still looked like:
I guess if you just leave your car in the garage for a long time and finally returns, you should be expecting to meet your car in a well preserved body paint...