Your 9 miles is a good compromise distance for the bike ride, long enough to feel like a real ride but not so far as to wear on you. When I was commuting 9.5-10.5 miles I often wished for four or five more miles, just for the ride, but you know lots of times you just want to get to work and shorter is better.

From that perspective I think that a little shorter is ideal. Mine is 7.8 miles door to door, almost a mile of which is parking lot, short for a workout but at 25 minutes just about perfect for a commute.