... are you not at all more productive the week right after a holiday than when you've been crunching for 5 months straight with no time off? Because I bloody know I am. Knowledge work really can't just be conveniently bundled into units of productive vs unproductive time like making widgets.
There’s no quality evidence that reducing hours worked below 40 hours increases productivity per hour.
All research done to date shows that productivity per hour is flat until about 60 hours or even higher for low skill work.
What you’re doing is called motivated reasoning. You want to believe that you can work less and still get the same amount done, so you cling to whatever nebulous explanation you can find to support it.
The reality is that you work less hours, you get less done.
