I'm convinced that if anyone wants to develop software for the rest of their lives, you have to do it carefully. The activities associated with writing software (typing, sitting, staring) aren't natural. This also applies to other computer-intensive activities, like gaming. You must be proactive in mitigating the negative effects of this pursuit or they will eventually bite you. I know of so many young developers who have terrible ergonomic setups. They are just asking for carpal tunnel and other nasty surprises in 10 years. I myself have mild carpal tunnel in my right wrist, initally brought on by my irrational love for the original Tetris.
To this end, I have developed some defensive tactics for interacting with a computer. First and foremost, the Natural Keyboard. In fact, I was very attached to the orignial Natural Keyboard from Microsoft, then they changed it on me, ruining the placement of the meta-keys. After some chagrin, I switched to the Natural Elite (which has a different but less obnoxious arrangement of meta-keys). Because I want to type on the same keyboard, I bought 3 of them (1 for office, 1 for home, and 1 for the road). I hate typing on laptop keyboards!
For mousing, I generally use my left hand when I use a regular mouse. When I must, I use my right (although it causes discomfort if I do it several days in a row). I recommend that everyone learn to mouse with both hands and switch out periodically (like once a week). I know it's annoying to learn, but it doesn't take long and it becomes second nature. I've tried several mouse alternatives, the latest being an iGesture pad from Fingerworks. I had tried one of their keyboards a while back but it was too much. The iGesture pad is brilliant. It looks like a mouse pad, but it's fingertip sensitive -- different combinations of fingertips give you different functions. So, it not only replaces the normal mouse functions, but allows cut, copy, paste, zoom, and a whole bunch of other functions. Best of all, because the movement isn't restricted to a single plane, I can use it with my right or left hand with no discomfort. It's pricy, but well worth it. Most of my mousing now is done on the iGesture pad and I love it.