Iím sure this question has been asked many times but the search function for this forum sucks and the question has not been asked recently. The question is, how thin can I let the sintered pads get before I need to replace then? Are they glued on to the backing plate where they can go to a fraction of a millimeter or are they attached in some other way? Or is there some indicator where they will make noise or some visible indicator that lets you know when to replace them? The manual is worthless on this question and since the pads are bedded into perfection I would prefer to not replace them until it is necessary.