For me, it depends on the intensity of my workouts. When I was 220, I could only walk a few miles (back in August of this year). Now that I am about 177, I can run several miles, and I log about 6-7 miles including my warm up and cool down walking, running about 5. If I do this 4 days in a row, I take 2 days off. It seems to work for me. When I was training for sports, we trained 6 days/ week, and that was the best shape of my life. I think you have to see what you are comfortable with. If you are dragging yourself to the gym after 5 days straight, may be time for a break....