When the UV inhibitors break down, you get the chalky residue on the vinyl and painted surfaces. That is why every so often you need to repaint. Vinyl..... not much you can do but do restoration and that is costly, not many would want to do that. That has been talked about here a while back in some threads.
Some people have painted vinyl but then you get to the same thing as if you had never bought the vinyl, you have to start painting again.
Until you have a great solution and restoration method for the chalk on surfaces, it is usually more hassle than what the job is worth and when the job comes out uneven, you are responsible and could end up in court, easier to just walk away.