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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