[Tekhne]

I wish I still had the links handy, but there's over a century's worth of research out there showing that it's a bad idea to go over 40 hours in a workweek for any extended period of time.

Of course, everyone's different, but I've noticed I have 4-6 hours of productive time in me per day for knowledge work (e.g. programming). I'm guessing I could get multiples of 4 provided there were long breaks in between, enjoyed what I was doing, and wasn't constantly being interrupted.

[DaniFong]

Perhaps this is true in a corporate environment, but some of the more productive periods in, say, open source development, or research, are pretty much whole life affairs. Einstein's Annus Mirabilis, for example.

[gaius]

No-one can sustain crunch time indefinitely.

[DaniFong]

I agree, but it's never crunchtime when curiosity drives you.