My dad has an E-350 7.3 that he uses for passangers mainly. Some Hauling, some towing.
He just had balljoints replaced not too long ago, I think a tie rod, and some other misc. parts replaced. He's got Bridgestone Blizzak snow tires on it right now, and these tires are extremely soft, so his tires are getting some wear on them. But nothing severe.
Mainly, are you keeping your tires rotated? There's a LOT of weight being carried on the front tires with these vans. Is the front End TIGHT??? No loose components, Balljoints, tie rods.... ANY Amount of play on those will throw your alignment out...