I came across an interesting post on Dan Schawbel's blog about ROWE - results only work environment. The idea is that we are owe our employer our results, not our time. We work when we want to in order to get our work done. No more 9-5 (or 8-6 as some organizations are).
I've worked in a couple of places where the emphasis was how long you worked, not what you delivered. The smarter companies are recognizing that isn't what's necessary in this day of knowledge workers.
Last Friday my kids were off school. I got up early and put in a very productive 5 hours. Then I went mountain biking with my son, took both kids to lunch, and went back to the office to wrap things up, another 3 hours or so. Some days I will wrap up before 5, go for a run, and then spend a little time answering emails before I go to bed.
Now I will admit there are some days, especially when I'm with a client, that I'll put in 10+ hours in the office. A flight attendant accused me of being a workaholic this week because I was about the only one not sleeping on an early morning flight, but to me, the airplane is a great place to get things done, no distractions. It helps when I'm in first class and have a little room to spread out. It also means I don't have to work late at night and I can go out and enjoy myself.