There's an elephant in this room. Are you all ignoring it deliberately? Reading all these comments from people about what they do/don't do. Nobody seems to address the giant stinking pachyderm: are you right or left handed? Left handers have to exercise their right hands, because of all the kit made for the right-handed majority. Almost all these fancy vertical mice are right-hand only. In fact most mice are RH only.…
I'm left handed, but I very early on (ie. like around age 5-6) I switched to using my right hand with a mouse. Since getting wrist pain in my right hand, I've purchased a magic trackpad which I keep to the left of my keyboard and I alternate between left w/ touchpad and right w/ mouse. It's worked very well for me!
What's interesting is that it's not as hard as it sounds. You basically just reverse your left/right click settings and your brain picks it up very quickly.