Wheel spacers aren't any worse for wheel bearings than wider wheels. Wider wheels and wheel spacers certainly add more stress to the wheel bearings, but you'll hardly ever read of wheel bearing problems on these trucks. Spacers are nice because you don't have to get new wheels, but they cost more (than a set of steel wheels) and there is some extra maintenance. You need to check the torque on the extra 24 lug nuts periodically, and that requires that you remove the wheels.
Wheel spacers and less offset wheels both put some extra stress on the spindle and outer wheel bearing.
Things are designed so that the load of the vehicle is placed on the inner (larger) wheel bearing that is closest to the knuckle so there is the least leverage on the spindle, then the outer (smaller) wheel bearing is mostly just for centering things.
Wheel spacers and less offset wheels move the load to the outer wheel bearing and puts more leverage on the spindle.
Now with these trucks the wheel bearings are almost the same size so I wouldn't be worried about wheel, bearings self destructing, just be sure to repack the bearings every 30K. Though I would be a little worried about the added leverage and stress on the spindle.
But I've never heard of someone braking things or running into problems because of wheel spacers and less offset wheels and I will be going the same route too soon.