12 miles each way here (35-50) minutes depending on direction and the wind). I'm not sure what my upper limit is. Probably an hour each way. Come to think of it during the last stretch of bad weather it was taking 60-70 minutes each way and that was starting to be a bit much.

The two main reasons to avoid a long commute are its too hard and it takes too much time.

Regarding the first, you can build up to it over time. After a few months it won't be nearly as hard.

Regarding the second, for me at least commuting saves time. Not because I can't get to work faster by (car is about 15-20 minutes faster), but because I am combining working out with going to work. If I went to the gym in the morning and then drove to work, it would take much longer than simply riding to work.

Paul