I ride 11.5 miles one way and my route is pretty flat. I can ride that distance in anywhere from 40 minutes to as long as 50 minutes, depending on wind, or other weather. If you're saying you can ride 12 miles like it's nothing, just give it a try one or two days a week and see what you think. You might eventually get like me and feel like you're cheating if you get to work any other way than by bike.