Our E350 coupe (a C-Class in a smart suit really) does just under 20k miles per year.
It's 3.0 V6 TDi gives all the tractor/caravan/dawdler-skipping rocket power we need as well as a nice quiet cruise.
We've just clicked over 100,000 miles.
Other than scheduled servicing (by a Main Dealer during warranty then a Mercedes specialist) and tyres we've only had to shell out for a set of glow plugs, though we've just had an advisory on slight corrosion on a brake pipe and a small split on a CV boot.