I've been having Blackstone labs run oil analysis on my E320 Bluetec after 10K mile change intervals. This car has a DPF, so requires a low ash oil. I use Mobil 1 5w-40 Formula M ESP.

In short, the oil holds up fine for 10K miles. Wear materials (mostly iron) are linearly higher from numbers seen at shorter change intervals. Viscosity is fine, insolubles are fine, additives are still within acceptable ranges. Because the OM642 uses post-injection to regenerate the DPF, the fuel dilution is 3.5% over 10K miles.

I suggest you send in a sample to Blackstone at whatever mileage you are comfortable with. My guess is the results of an analysis will point out that MB engineers actually do know what they are doing and the FSS intervals are fine.