I work P/T (four days a week)
I try and get a couple of hours done a day on the days I work and between 5-6 hours on two of the days I have off (usually I try and have one day off, but if I'm a good girl I'll work for a couple of hours then too)
So overall, I probably get around 20 hours of work done a week as a PT student (saying that, I have some weeks of complete writer's block and don't do ANYTHING!)