Since leaving my last job, I've been working seven days a week, but at my pace. Lots of breaks and downtime (naps, even), and I don't mind taking full days, every now and then.
Amazingly, I get more done, in less time, than I ever did before.
In Japan, the traditional salaryman workweek is 6 days, with Saturday being "casual," and sometimes, a "half day" (only 6-8 hours).
We'll have to see how this works out. Lots of cultural hysteresis.