"Nobody can continually do creative intellectual work for over forty hours a week. Your effectiveness will decline sooner or later."
I don't think so. I think this depends a) on motivation and b) on individual capabilities.
a) I know this from watching myself. If I work motivated on a project, I can work long days and enjoy the progress.
b) I know this from watching myself. When I was in my twenties I worked full time and studied and cared for my family. I did not feel tired all the time. Today, in my fourties, I feel tired in the evening and am happy to enjoy spare time activites. So if you mean by "Your effectiveness will decline sooner or later" "at least when you are fourty." then you may be right. But that does not mean that a twenty something should not work more than 40 hours if she is willing and capable.
I agree with you in both cases, but:
a) I also can work 50-60 hrs/week if I like the project. I even did 80. If I don't like it I still can, it just frustrates me in that case. But it's not about just doing the stuff. It's about how effective you are when time passes. If you are a good dev, even if you are not effective you still see the progress.
b) When I was at the University I could go on much longer, that's true. But then I also knew that I can play hooky if I needed and I had a vacation once a year and all those long breaks for Xmas and so on... How long you go on like this really depends on your fitness. But can you go on like this all year round? Sooner or later you'll need a break, a vacation, or just quit. If not, you are a superhuman (and I am sure my mum is, even though she's not a dev) ;)
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