The optical mice last much longer than the old roller-ball mice
Mechanical mice here have really lasted more than five years but, then again, every Sunday they get disassembled, cleaned, inspected, and where necessary lubricated. Optical mice really depends on when the optical component succumbs to quantum failure. They get the same routine for the switches and sensors cleaned, but I have yet to break out the soldering iron to fix 'em given component cost. I do still miss mi Amiga's Boing! Mouse. The optical in that lasted a decade.
As far as the laws of mathematics refer to reality, they are not certain, and as far as they are certain, they do not refer to reality. -- Albert Einstein