The balance is absolutely essential. I believe in it so much that I picked the URL for my business to keep it in mind always: buildandbalance
I find that having young kids forces me to have balance in my life in that there is no way I'm going to neglect them when they're around. I make sure to take the family out to dinner once a week, do some kind of activity every weekend, and be there for all their special events (well, almost all).
I'm sure that if I wasn't a family man I'd do the same, but with friends instead. Life's just too enjoyable to work only.
By the way, in my workshops one exercise I ask owners to do is to write out your tombstone. Seems morbid, but it gets them to face what they want their legacy to be and it's usually not 'she worked hard'. Thanks for the stimulating article!