As a guarantee, good will does not expire once a certain amount of time has passed. To give credit where credit is due is the essence of good will. It seems like you're far beyond the coverage of the new car limited warranty, which usually covers paint defects for three years or up to 36,000-50,000 miles on a Mercedes-Benz of that age. They were not required by law to make any kind of offer, and I'm not even claiming it's fair, considering that it's been eight years.