I'm not sure, and this is why.
Many jobs require marginally insane hours, as many jobs require attention on the weekend and during other purported off times. An academic job requires insane hours at times and makes the distinction between time on and time off blurry at best, but the killer is that so much of the success of an academic job depends on the individual holding the job.
A lab makes or breaks because of the ideas of individuals: initially the PI's and later other members of the lab as well. Grant money is awarded to an individual based on their ideas and their ability to sell their ideas. Individual charisma goes a long way to making a story sell-able, how much more likely are you to remember a PI who gave a fantastic talk at a meeting? And how much more likely are you to be accepting of a bumper publication on that topic? The personality, drive and energy of the PI are critical to the success of a lab, and on a smaller scale, the personality drive and energy of a postdoc (and to a lesser extent a grad student) are essential for visibility, contacts and eventually a job.
Here I must say that I think balance involves a certain degree of dissociation from the job, but this is personal and may not be the case for others. With dissociation comes relaxation, perspective and professionalism, all of which make for a happier work experience. The things is, I cannot see how dissociation goes with the extraordinary degree of personal commitment that an academic job requires. The very basis of a successful academic career is an intense driving personal involvement, or at least it is in all the Biology labs in the United States that I have seen. So I don't if balance is possible with an academic job-in Biology, in the United States.
Do I have it wrong? Have I just worked in really intense environments? Which I have loved by the way, I love the buzz of achievement under pressure as much as any one. Is it different in other fields? Do I have an unrealistic view of academic positions? I don't know, and would to like to hear your perspectives, because I am increasingly coming to believe that an academic position in today's environment may not lead to the kind of balance that I believe is necessary.