Many years ago, a french magazine conducted a large scale survey of the number of repairs their readers had had per camera, cost of repairs, etc. Two cameras came well in front of all others: the Nikon F and the Pentax KX. Both at 0,69 (F) and 0,70 (KX) repair per 100,000 actuations if I remeber well. KX was the pinnacle of the development of the Spotmatic, with K mount + SPD cell + mirror lock-up.