With typing and data entry jobs, how often do you take breaks?

I've got my typing and data entry speed up to an acceptable level, but I'm worried that I might not be able to hack doing it full-time. I mean when you're practising at home you can take breaks etc. It's not like you're going to get there and try to do it for a whole day! But perhaps this would be a good idea to try. Any advice?

With typing and data entry jobs, how often do you take breaks?
I take a 30 seconds break every ten minutes, by rotating my wrists quickly, control your blinking, etc. Make sure your supervisors don't think you're lazing around, so do not be obvious.