Nikons don't need it nearly as often. They went above and beyond with components of great quality and, and god I must emphasize this, inorganic lube. That makes a lot of difference. F2's in particular are held up as an exception to most rules about camera maintenance. I would say CLA them once every 70 to 120 years... and most of them are in their early to mid 40's... only about twice my age and I'm used to cameras older than my grandparents.
And yes, I'll say it: Nikon's best is better than the majority of Leica equipment. An F2 is a smarter investment than any rangefinder camera. It can use a far larger variety of lenses, does not need special attachments to accurately focus extremely long tele lenses (though a very cheap focusing screen can help), can meter macro photography thru the lens, top speed of 1/2000... and basically never needs maintenance if treated well.
This does not mean that precisely-made German cameras with organic oils do not need a CLA every ten or maybe every twenty years if you want to push it. Those oils seize up, solidify, flake off and jam up gears. By the time the shutter speeds are getting wonky it is probably too late to save the full lifespan of the camera, whether or not a CLA can restore functionality in the medium-to-short term.