Really depends on what's going on that day. It can range from 4 hours on up to 10. I'm loving what I do so it's no worry. The best part of it is at the flip of a switch, i can up and do what I want. The freedom is amazing.
I'm a writer and I work maximum 7 hrs daily, which I think is more than enough for me. Living all your life merely for making money is worthless if you're not enjoying your life with it.
At first i used to work 10 Hours a day. Now i am not even working 15 Hours a week.. I am allotting all my work to my staff and i am enjoying my life.
I work for about 12-14 hours per day. I try to keep busy in job and exploring new avenues as well learning new things every day.