How do you clean them? For the MX master, the worst bit to me is the rubber inside the scroll wheel(s).

Re. breakage, one was almost certainly my own fault with transporting it too much / carelessly (primary scroll wheel could no longer enter the “clicky” mode), though I’ve also had the sensor for mouse movement fail on another one (those two are the ones I recently “merged”).

I’ve owned three or four MX Master mice. That statement alone should show pretty clearly that it’s not a “buy it for live” device. I did manage to merge two broken ones into a working one recently, but I don’t expect it to survive another 10 years.

One of the major problems even if nothing technically breaks is the rubber coating getting greasy or sticky with time. This rubber coating is unfortunately also used in other logitech mice, especially the more expensive ones.