4th D600, same problem.

Fine, yes, don't smoke in a $100k car. that's a user caused condition. for the D600 oil spots, the better analogy would be to complain that after buying an expensive car, you still have to change the oil, wash the wind shield, and rotate the tires.

Performance materials require maintenance.

Yes, you have to have the oil changed in your ferrari after a race, break down your rifle and clean it after hunting, and have your Armani suit pressed after wearing it.