Our trucks are different than most. In our case, when not in 4x4, the front axle sits still and the wheel bearing hub (and spindle bearing) rotates around the axle. Therefore, the spindle bearing is always running. On most other trucks, unless you are in 4x4, the spindle bearings are just holding up the axle, but not turning.
As far as damage, your vibration is a problem (as you already know) because eventually it will trash your locking hub as well as cause the axle shaft to "vibrate" in the 3rd member. What kind of long term damage that could cause, I don't know, but it can't be good for it. As far as loosing a wheel....I don't see that as an issue.
