I have a 12 mile commute. I could shorten it by 2 miles if I wanted to, but it would mean traveling on busy roads, rather than bike paths and quiet residential streets for the majority of the ride.

Sometimes I make the tradeoff, on my way home, and I really feel like letting it loose and riding top speed the whole time. It's a straighter shot, with less lights/stops along the way. And I generally feel safer at higher cruising speeds as I'm nearly keeping up with traffic for most of the way.

Most often though, the tradeoff doesn't make sense. I'll trade the 2 miles for a significantly quieter, safer, more pleasant commute.