I'm thinking that we're talking about different things. I like my family and want to spend time with them, so I don't plan on working 100+ hours a week. It just isn't worth it to me, even though it would probably make me more productive/successful. If I didn't have kids, I would probably just spend all of my free time at work because that is just how I am, but it's not an ego-driven thing. I want to be a scientist and a doctor because I think both of those things are fun, and having a successful career is what facilitates that particular kind of fun. It would not be fun anymore if it prevented me from having meaningful relationships with the people I love.

Perfect example: my advisor got divorced during his training because he spent nearly all of his waking hours either in clinic or in the lab. He remarried after residency but kept basically the same schedule, and he didn't realize for three years that his kids played little league because he saw them and talked to them so little. He looks on it as almost a point of pride, and he said that the difference between the big fish and the small ones is about 30 extra hours of work per week. He is super successful and productive, but I would never want to be like him.

Even prioritizing my family, I still do a lot. When I was finishing up my PhD, I would generally work from 7:30 AM-5 PM on weekdays and do either two half-days or one full day on the weekend. I did very little work at night unless the kids were already down. Could I have done more? Definitely, but I am happy with my productivity (5 first-author publications, 12 contributing authorships, multiple fellowships and small grants, presentations at national and international conferences). Likewise, in medical school I am substantially above average on clinical evaluations and test scores, but I try to make sure I spent time with my kids in the evening and on weekends. I could work harder and probably eke out a few more points on my shelf scores, but I am already getting honors. On the balance, I feel like I'd lose more than I gained if I traded those few hours of kid-time for study time.