Perhaps this is an issue of quantity vs. quality.  In education we are thinking hard about whether the things we do create healthy, productive citizens or stressed out, worried kids.  Homework is one example.  How much is too much and is it work of value or just work?

Business might think about this too.  Are your workers most productive, innovative, and efficient when they are exhausted.  Of course not.  Just as we need a new metric to measure effective teaching, perhaps we need a new metric to measure effective work in our own workplaces.  We need to measure more than just hours of work in order to assess value.  It assumes that every person does exactly the same amount of work in each unit of time, a concept that is clearly false.