For example, I use workrave with a 25 second micropause every two and a half minute, and a 10 minute restbreak every 20 minutes. I need these frequent breaks, because I’m recovering from RSI. And as I recover, I change the settings to fewer breaks.

If you have never had any problem at all (using the computer, that is), then you may want much fewer breaks, say 10 seconds micropause every 10 minutes, and a 5 minute restbreak every hour.

It is very hard to give proper guidelines here. My best advice is to play around and see what works for you. Which settings “feel right”. Basically, that’s how Workrave’s defaults evolve.

Any pointers to more scientifically founded advice are of course very welcome :-)