My daily commute is almost excactly 10 miles. Although if i'm feeling particularly weak, or it's cold, windy and rainy, i can take light rail, and shorten it to just over 4 miles. Similarly if I'm feeling especially energetic or adventurous, i have a route that is about 12 miles, but much more scenic (and more elevation)
That's all each way, so often I mix the routes up. Since it's slightly downhill on the way to work, I'll often do the 12 mile route in to work. If it was a long day at work or the weather turned foul, i'll take light rail and do the 4 miles commute home.