About 14 months ago the mounting tabs rusted off one of the rear disk pads. A local shop changed them for me (it was winter).
Yesterday one of the rear brakes started to make noise. Today I pulled the pins and the metal bushings and found that the shop had failed to either clean or lube those parts. A little cleaner and synthetic brake lube later all the noise was gone. Apparently the calipers had started to hang up.
Richard.