Yeah nell-again, I can sympathise with you, but I don't think it is our Mouse but our "AGE", sometimes even the Elbow hurts, especially before the Weather changes!
I really envy People who started on Computers early enough to remember all the Shortcuts, hence very little use of the Mouse.
Alas, my remembering Shortcuts, bar a few is impossible
Have taken Neons Advise and lowered my Chair to change the Position of my Arm/Hand on the Mouse, I can not get the Chair down low enough, but even lowering the Chair a little bit, made a Difference already.
Will get my H\B to look into it, he is pretty handy with a Chainsaw, if all else fails.
Oldyellas Mouse looks great, but do not like the Idea of having to have 2 Mices!