In the same situation I think my productivity is actually equivalent with fewer hours after having kids because it has created an ongoing sense of urgency to ge

In the same situation I think my productivity is actually equivalent with fewer hours after having kids because it has created an ongoing sense of urgency to get done what I can in the 8:30-5:30 window. In the old days, 4pm was almost like the half-day mark, which personally led to a mental slackness about how much time I had left to accomplish a given task that day. These days, I sometimes get cut out of the zone by quitting time, but more often than not I am mentally exhausted and ready to go. I'm sure that this would not apply to the most focused and driven programmers, but I'm also sure that a lot of young startup types are fooling themselves that the long hours they put in are giving them better returns than they would get with a bit more sleep, a bit more exercise and a bit more downtime.