for me, 13 miles is perfect. I get it done in under an hour in optimum conditions, and under adverse conditions it's still doable. it's perfect for nutrition and hydration reasons too. not to mention in the winter longer rides would result in a frozen water bottle. also an hr of exercise is worth the hassle of commuting clothing food washup routine etc etc. however if I got a new job 9 miles from home I would jump at it!