Well hey now, let's do the math. If he sleeps 6 hours at night, that gives him 18 hours a day to walk. 20 miles in 3 days, 18 hours a day, means he has to walk at least 0.37 miles per hour. Do you really expect anyone to be able to walk that fast? Edit: and if he sleeps 8 hours at night, he has to walk 0.41 miles per hour! Oh no!!