Never tried the Expert Mouse in particular. Two of mine were slimblades, one orbit with scroll wheel. Different failures each time -

Orbit - broken plastic around one of the bearings. ball no longer turned smoothly or straight in every direction, and dragged. Slimblade #1 - began to operate erratically. I believe it was a failure of some kind with one of the optical sensors, but I never was able to figure it out consistently. Slimblade #2 - microswitch under the LMB failed mechanically, no longer triggered.

the slimblade's were provided by my employer at the time, the orbit was purchased personally for at home - it's use overlapped with the slimblades at work.

I don't think I'm super unusually hard on my trackballs - My Elecom Huge lasted for ~6 years before the soft touch plastic finally got a bit gross from skin oil contact, but still was functionally fine, and my current protoarc is going strong two years in.