My mouse is 19 years old
It's a Logitech M-BJ58 optical scroll mouse that I bought at Best Buy in 2001 for about $20 to replace the crappy non-scrolling ball mouse that came with my first crappy PC (eMachines). I've used it pretty much daily ever since.
In 2007 the original microswitches were getting flaky, so I desoldered them and soldered in some new ones.
In 2015 those replacement microswitches started getting flaky so I replaced them again.
A few days ago the scroll wheel started acting up, sometimes working perfectly and sometimes not working at all. I don't know where to get a new photoelectric sensor/switch for it, so in the meantime I resoldered the existing parts and cleaned them with isopropyl alcohol. Also, the left-click microswitch was getting flaky so I replaced that tonight too (the other two microswitches are fine because they don't get used as much, plus I only had one new microswitch onhand anyway).
So far so good. All of its functions are working perfectly right now.