Our small (24 foot) 2005 E450 Class C motorhome has 73K+ miles on it - with the original front brake pads that my mechanic measures as still OK.
I attribute this long front brake pad life to at least these two things:
1. Underloading of the E450 chassis in that our small rig is usually built on the E350 chassis. The E450 chassis has larger brake swept areas than those of the E350 chassis.
2. I try to travel most of the time with it's transmission in Tow/Haul mode. In this mode, engine braking is used when slowing for any reason, plus whenever traveling downhill. This reduces wear of the front (and rear) brake pads over time.