I know someone who used to often commute ~30 miles round trip on a Brooklyn Race Link!
At one point in my life I had five bikes. (I know, I know, but money was tight), so I decided I would cycle into work each day (about 15 miles each way), on each bike in turn.
Monday was fine on the road bike
Tuesday on the cross bike was also fine, fun even.
Wednesday on the Geared mountain bike, fine
Thursday on the singlespeed bike, fine but a little tiring
Friday on the singlespeed jump bike.,,, Mother of god! I thought my legs were going to fall off. So, so tired when I arrived at work but by the time I got home I could barely stand.