I generally wear out fronts and rears on the C230 at 60,000-70,000 kilometer intervals (37-43K-miles). The E300 has about 56K (35K-miles) and the fronts are at about 25% and the rears a little more.
MB pads wear faster than most cars. But, most MB cars stop harder than even Porsche models, so you need to ask yourself what your priorities are. Stopping or pad life?
1998 C230 "Black Betty"