Yiannis Konstantakopoulos, a designer at Porcupine Colors, wrote an excellent piece on workaholism.

Workaholism is often confused with hard work. Some people who work on the Web seem not only to disregard its dangers, but to actively promote it. They see it as a badge of honor — but is it really? On the contrary, it’s a serious issue that can damage Web teams. Before we get started, let’s make one thing clear: A “workaholic” is someone who is addicted to work, someone who is out of balance and out of control. Their addiction can make them work for 12, 14 or even more hours a day, every day. No weekends, no vacations, just work. Soon, they neglect their family, friends, health, sometimes damaging them all irrevocably.

https://medium.com/@porcupine/dealing-with-workaholism-on-web-teams-d6e156d82a08#.jyzawevsb