suprz,
You have Ford's 5-speed (6 ratios, internally) computer controlled TorqShift transmission in your 2006 E450 chassis.
Regardless of what you do now concerning a brake job, going forward you can get better brake life by leaving your transmission with it's Tow/Haul mode engaged full time when traveling. This gives you engine braking all the time - on the level whenever slowing down and stopping, and whenever controlling speed going down grades.
I have used Tow/Haul mode a lot in the past with our 2005 E450, and I pretty much use it full time now. At the ~60K mileage service point, some time ago, we still did not need brake work.
By the way, using Tow/Haul mode full time in an E450 based motorhome should yield longer brake service intervals than using Tow/Haul mode full time in an E350 based equivalent weight motorhome because of the more aggressive (higher) rear differential ratio of the E450 chassis. There is more engine drag when letting up on the gas in a vehicle with higher rear differential ratios.