I am still using my Nikon D4 (2012), but they simply don't make parts for it anymore. These are mechanical devices, so they will simply wear out with use (I got pretty much the last spare parts that existed in my country when it last needed servicing).
I find it a bit sad; I could understand it for a dinky plastic camera, but with a flagship device, why can't they just make a bunch of parts and put it on a shelf for 30 years?
Eventually I'll probably buy a mirrorless; but I guess with a shutter count of 196 613, it's had a pretty good run…