Most of the time the bindings are removed for grinding, and sharping, less of the time for waxing. On any of these race stock skis there is a plate attached to the ski which makes removal of the bindings simple to do. Even the plate is removed for grinding, so that stone pressure does not change over the length of the ski.
But you were also right that there is a constant supply of new skis. Alot of the skis showen here are speed skis, and generaly the "race room" will have many differnt pairs of skis, because some skis turn out faster than others and the only way to find those skis is to prep them and ski them.