The productivity/defect studies aren't about over the life of a career, it's about productivity in shorter time frames. Things well matched to this "make or break" scenario.
Studies about career length stuff tend to deal with worker retention problems and/or long term medical issues (such as depression).
For anyone interested, here's an article that does a good job of capturing a lot of the issues and results of studies. It's not a study, it's a Salon article, so it's intentionally a synopsis (well, the first 1/2 is synopsis, the back half is more a call to action).
Bring back the 40-hour work week - Salon.com
There's so many assumptions being made about 'people' in general, that I can't take any of it seriously. The article is being written as if all people are created equally; as if they are all equally skilled, equally devoted, equally motivated, equally intelligent, equally hardworking, have equal amounts of common sense, practicality, are affected by their environment equally, take care of themselves equally, have equal family/homelife/friend/relationships and support...and so on.
That is not the reality of 'people', therefore a study, an article, a synopsis, whathaveyou, is of no relevance. First, you'd have to start with a group of people who are equal in 'all' aspects to get accurate data that could be applied to all, and that's not possible.
Mental and physical tolerance for work is individual and based on an infinite number of factors. Mental, physical and emotional health is also individual and based on an infinite number of factors. We can make some VERY general assumptions.
1. When a person is tired their capacity for thinking and doing is reduced. How much, to what degree, at what point it kicks in...speculation at best and varies from person to person. One person's 10% reduced rate might still be 50% better than another's.
2. Working 60-80hr work weeks is not sustainable. But the non-sustainable point is different for everyone.
3. Having to do shift work is far harder on the body than a few extra hours done each week on a shift that never changes.
4. People love to complain about what's not going right in their lives, instead of being happy about what is going right. (Yeah, I know. Doesn't seem to belong, but think about it.)