30 here.
I don't know...maybe when I had to give up my Logitech G5 mouse at work (and at home) because it made my wrist and index finger hurt. I had to move to one of those vertical mice from Evoluent, which helps a lot. But it doesn't have as many programmable buttons. And it doesn't have the awesome scroll wheel. And it's mostly polished chromed plastic that accumulates dirt easily, and constantly feels sweaty or oily, unlike the G5's textured surface. And it's impossible to be terribly accurate with it, as the force needed to generate a click is parallel to one of the axes of motion.
Back in the day, in Quake3 Arena, I could usually get the Accuracy award, which I believe was 80% or better. I fired up Star Trek Elite Force again recently. I'm lucky if I can break 35% accuracy now. Usually it's closer to 15-20%. My weapon preference is now for things with substantial splash damage, as everything else is mostly good for scorching walls.:\
But at least my wrist doesn't burn in pain anymore, though my index finger still complains a bit.
:\
When the hell is medical technology going to progress to the point that we can start replacing pieces of evolution's cobbled-together design with something more durable? Nature says, "Ok, you've lived long enough to pass on your genes. You're no longer needed. You may die at your earliest convenience." We tend to have plans for life that go a little bit beyond that, as our bodies slowly come apart at the seams.
Otherwise, not a whole lot comes immediately to mind.
Maybe the ever-increasing number of gray hairs that show up when I'm getting a haircut? It's graying on the sides, so it's not always readily-visible when my hair's gotten a bit longer. As soon as it's cut, theeerrrre it all is!