I've been steadily increasing my mileage and my time on my stationary bike. I want to lose about 20 pounds. Today, I clocked in at 20.8 miles in 78 minutes. I'm wondering if I should continue adding time and mileage. Is there a limit? I feel fine. Is this normal to ride this many miles on stationary bike, or should I reduce and do other exercises as well. In addition, I've been walking 3.75 miles. Should I continue to increase my mileage on my bike? Is this OK?