It could be though that a 45-year-old has better perspective on what's important and what's not and therefore has better time management skills.

I know when I was first starting out as a developer I spent a lot of long days and weekends working but not really getting a whole lot accomplished. As I've matured, I've gotten better at picking out what's really important and am now much more productive while working less hours. I anticipate this trend to continue as I gain more experience.