Just so you know, Boyf has some serious mad skills climbing stairs with his knees. And yes, this is serious. If you've never tried it before go do it now, you will then appreciate how awesome this is. Also, try jumping on your knees; not using your feet. Go ahead, try it. If you get more than one inch of air check and make sure you are not using your shins or feet, it has to be nothing but knee. If you are still getting more than one inch send me a picture of it.
Here is a pic of Boyf. beating a record for knee-stair climbing. And as far as distance goes, the stair case was a pretty good size and fairly steep. I'd say he climbed about 20ish(give or take one or two) stairs.