As someone who owned a wide-belt sander, I would like to add that I would NEVER spend any of my time working with a customer to sand their crappy weathered top flat. It contaminates the belt with "whatever" and I run the risk of tearing a belt on "whatever" could be embedded in the top. All to make, what? 20 bucks?
Maybe you folks have found companies willing to take the risk, stop production, change settings, change belts, etc, etc., but in my shop no used material ever found its way into any of my tools unless I knew the history of the material first hand. I would overlook the rules for maybe my Mother......maybe.
Before I got my sander I used a friends. Even my friend required that I use my own belts on his sander...and he charged me time on the machine.