Well, to be fair, I do put a lot of miles on my equipment. This time, I just wore out the right button. I did remap the buttons (so now the left button performs the functions the right button has abdicated) and switched it over to my left hand, but it makes my brain hurt to use it that way. Probably a good reason for continuing, but lazy will, I fear, triumph. The UPS website reports that the new trackball is on the truck for delivery and will be in my hands by the end of the day.