I'd advise everyone to watch out for RSI or back problems. You don't know how bad it is until it happens to you. It can put you off work for more than a year.

Get to know the ergonomics principles and apply them. Do take breaks and stretch. Don't type or mouse excessively for long periods. Don't say it won't happen to me, and don't say that's impossible to do. When you find it impossible to work you'll wish you had made it possible to take a few measly breaks.

I've just started cycling to work, 1 hour each way. It's great.