Many years ago before a mouse had become the mandatory method of providing a computer with some of its inputs, I found myself in the radar room at EGBB ATC unit and was invited to have a "play" with their system. This was driven by a large, heavy trackball and I have been a fan of trackballs ever since having gone through quite a few since those days. The main problem seems to be the "click" switches developing contact bounce after a few years of use necessitating replacement. Although my first trackball was a mechanical one, the remainder have been optical ones and when they start to have difficulty responding, it is a moments work to pop the ball out of its holder and remove the offending fluff with a finger. This invariably resumes normal service.
P.P.