I'm tempted to say that newer cameras will be more reliable. I have cameras that date back to 1930s - like Welta Weltur - which I love and it still functions great. I did need to CLA it but nothing had to be replaced. So to me it was a well made item. Yet still, I understand that old things just get old. Old Leicas get worse simply by being old. Technologies they used at the time were not as good as they are now. Mirrors, coatings, beamsplitters - all these start to go and will need to be replaced - if possible. Sutters/curtains wear out. etc. Newer cameras are better in those respects. Metal curtains, new coatings, etc will last longer. Also, as experience shows - plastic parts last for a long time now. Not always, but often. So, all in all, I'd have to say Bessa R3M and such would be a pretty good choice. But my Hexars seem to be going strong without need for any CLAs. Meanwhile 3 out of 4 Leicas needed CLAs and repairs. So there...😉