painting rocker panels

I'm having some paint work done on my bumper soon, and while it was at the "shop" I thought it a good idea to have other work done at the same time. My rocker panels are showing some signs of rust formation. The guy says he can sand the paint off up to the edge (right below the door) and repaint. Any thoughts on this? I don't have a problem with it because the "seam" would be on the edge and not visible.