In general front brakes account for 75% of the braking on most MB's.
The mileage that you get depends on driving style. My wife goes thru brake pads twice as fast as I do as she is always on the brake pedal.
Also as you can guess the compound of the pad does affect the wear.
As far as OE quality pads go I've found that Textar pads last longer. MB uses Textar on the rear of most newer Benzes
MERCEDES Benz Master Guild Technician (6 TIMES)
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44 years foreign automotive repair
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MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)