I have owned half a dozen Leica M film cameras, all of which have been used, not fondled. Every single one has required service of some type. Two required shutter curtain replacments, all have required rangefinder adjustments, some have needed the shutter speeds tuned up.
My old Nikon F and SP cameras have seen far heavier use than my Leicas, my oldest SP was a newspaper camera, and has seen thousands of rolls of film, the anodizing was worn off the pressure plate. It has worked for 50 years without repair or adjustment. My oldest F has been used nearly as much. The slow speeds are a bit off on the F, but it has never required repair or adjustment.
I love Leicas, which is one of the reasons I continue using them, but the old Nikons are mechanically far superior.