It used to take me over an hour to commute to work by car or an hour and a half to commute by train. At that point, I moved closer to work.

Now that I'm biking to work, I'd consider anything less than seven miles to be too short. Right around 10 miles seems perfect, though at that distance I need to change clothes when I get to work. If I had to bike in my casual work clothes and not change, I'd probably want a ride around 3-4 miles, but it would make me sad.