there is no reason for a more modern, post-85, Merc to have bad paint, IMHO.
Not always true. I have a 1986 560 SEL with 130K miles that is in excellent condition. However over the years the car had picked up some small chips on the front end, some door dings and scratches and a few faded spots on the hood, so I had the car completely repainted by a friend who owns a body shop. He did an incredible job using only top quality materials. The car is now in showroom condition. It was worth it to me to do the paint job as I plan to keep the car for many more years. Most owners would probably have thought the paint was still fine...but I wanted it perfect, thus the repaint.