I started bike commuting a couple of years ago with a 40-45 minute, 9 mile commute (one way). Since that time, my job location has changed and then we moved, bumping my commute up to an hour (14 miles) and finally to an hour and 20 minutes (19 miles). I never would have tried to ride 19 miles one way initially, but I now find it to be not bad at all. In fact, I am almost always looking forward to my ride to work on Monday morning after not getting in any good riding over the weekend.