Not sure what you mean by "valid". If longer hours lead to less productivity, why would anyone argue for it?

There are professions that have 12 hour shift. There are also companies that allow their employees to work 9 hour days and take Friday off every other week. Employees may even prefer these schedules for personal reasons despite potentially increased health risk.

Medicine is famous for 12+ hour shifts. However, it's demonstrable that this costs peoples lives as people make more mistakes in hours 8-12+. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4629843/

Hospital shifts in the United States should be used as a warning for what not to do:

"Halsted promoted several very important concepts and practices in residency training: graded responsibility, a variable and lengthy training period, a pyramidal system of promotion, a resident's ward service, and, most pertinent to this article, a restrictive lifestyle. This last concept of a restrictive lifestyle meant that residents truly resided in the hospital. They received little or no pay, were discouraged from marriage, and worked 24 hours a day, 7 days a week, 365 days a year. At first, the Halstedian model was more the exception than the rule but gradually became more common, especially after World War II when more surgeons wanted to be trained and certified for both the prestige and financial rewards."

https://jamanetwork.com/journals/jamasurgery/fullarticle/392...

The Halsted is William Halsted, a workaholic lifetime cocaine addict: https://en.wikipedia.org/wiki/William_Stewart_Halsted

Yeah I think this is for office workers. It's also useful as a baseline for overtime pay though. Even professions that work 12 hour days still pay overtime over 40/week. We could move that back to 35/week and let workers and employers decide if it's worth cutting back hours or hiring more people to reduce overwork and overtime pay.

I haven't worked at many places that don't argue for more work - doing extra stuff on the side, on-call shifts, there's always something.

"Remember 40 hours is the minimum we expect of you. Overnight installations are just part of the job."

It seems hard to look at the US and argue we aren't working enough.

We are certainly at work for long periods, but are we working enough?

Productivity is historically high. Yes.

No one ever argues we should all try to gain 50 lbs either. Both are valid possibilities.

Overweight people apparently live longer.

Is there some kind of skew here?

Like 1 million malnourished people in Africa dying fast vs 1 million somewhat overweight software engineers with healthcare benefits?

So what happens when you factor in fit people (which the US is probably short of anyway)?