We were told at enduser training that the Rotex sanders were designed to hold up to the abuse of sanding fiberglass wind turbine blades.
It was said that the sanders they used before the Rotex were lasting less than a week. The Rotex sanders did not fail.
I have sanded a lot of metal & solid surface material with mine & not had any problems. As for the vac. As long as you are using a bag & filters it will have no effect on it.