For years I have used this mouse, 3,000 hours of Arma 3, 700 of DayZ and many many more from other games. When the cable eventually breaks, I will fit a new USB, when the switches turn to mush I will solder in new switches.
I’m far from a fan boy, especially when it comes to Corsair but the Scimitar, best mouse I have had.
If you can solder I’d say most mice are easily fixable. The most common defect for mice are the switches, which are usually quite simple to desolder, as there aren’t any components near them.
E.g. I don’t have much experience soldering and it took me under an hour replacing both switches on the G Pro Wireless as well as the battery. I’ve bought this mouse used about 5 years ago and I wouldn’t be surprised if it lasted another 5 years.
Edit: The annoying part is the screws being below the feet, so you have to replace them after opening the mouse. But it’s all screwed in.
In addition to that, for popular, “name brand” mice, there are often also tons of replacement parts available from China. You can basically re-build the complete mouse from parts.
Otherwise, as you’ve said, switches, wheel, the battery and maybe the cable, should always be replaceable (as long as you can solder).