My predicament matches yours.
The new car salesman @ the Mercedes dealer where I bought the 2011 e350 Sport a while ago told me that people don't like to buy used cars over 100,000 miles, or over 200,000 miles.
So if the resale value is a worry, sell it now, for some dollars more.
Otherwise just keep driving it.
My 1991 560SEC AMG, (seen below) that I bought certified pre-owned from a Mercedes Benz dealer in Southern California near Disneyland, back in 1996, now has EXACTLY 199,457 miles on the odometer, so my predicament is exactly like yours, but, I have put a fortune into it, in repairs, upgrades, accessories and maintenance, and almost certainly will let it roll ove4r to 200,000 and then enjoy it some more.
It was my "someday car" from the day back in 1985 I drove the nearly brand new boss's 1984 Lapis Blue euro spec 500SEC AMG from San Francisco, where I lived, to Denver for him to drive on his Aspen skiing vacation.