> More time is more stuff.

That's the Taylorist position, but I think Deming would like a word. And in the more sophisticated manufacturing world with shorter more bespoke runs, the problem-solving ability of your employees and their time spent performing non-recurring setup matters as well.

> Most manufacturing jobs is done on a conveyor belt. More time is more stuff.

The 40 hour work week actually comes to us from research on the original assembly line. Henry Ford's analysts apparently concluded that 40 hours was optimal for overall productivity. Past that point and the cost due to the greater number of human errors more than canceled out the additional work.

I would wager that this optimal number is different for different people but also for different professions. In professions where fatigue doesn't result in more mistakes or mistakes are cheaper to rectify then the "optimally productive" hours per week might be higher. In professions where fatigue results in even more mistakes and mistakes are more expensive to rectify then the reverse might be true.

And this says nothing of the leverage of the workers themselves -- I suspect software engineers can get away with working fewer hours if they want to due to the fact that they have more leverage than most workers.

Also not true with manufacturing (btw software engineering is manufacturing too). More time = More errors = More damaged Machines = Worse QA etc....it's the same as with software.

Many factories, utilities, and other tricky hw like 24/7 b/c less restart errors

Blind men and elaphant? :)

Hospitals prefer 12 hour shifts for similar reasons. Their "restarts" are called "handoffs". A tired nurse in hour 11 of their shift is less dangerous than a fresh nurse who doesn't know everything that didn't make it into the patient records. There's a large body of research into handoff errors, and the lessons have mostly been put into practice. Unfortunately, this doesn't seem to be the case in "knowledge" based industries where failure isn't as easy to measure as death and malpractice lawsuits.

Wouldn't the handoff suffer more at the 11th compared to the 8th hour. I wonder if they take employee constant sleep deprivation transferring into patient experiences vs legal coverage when making these decisions.

The trade-off is whether patients see tired staff vs patients rotate through more staff with no context (= multiply chance of onboarding mistakes, more delays, ...). Tempering this a bit, a lot of smaller-staffed late shift care is more about handling emergencies and otherwise keeping folks fine until the bigger day shift comes in.

Most software IT/ops is luckily generally much smaller in time scale of most incidents, and much more tolerant of hand-off errors and delays. Ex: For 24/7, you get an instant email acknowledgement of ticket receipt, someone triages it, and if on a boundary, OK for current shift to ignore and leave for the next one. Likewise, for bigger incidents, better for throughput for the same person to pick across shifts to avoid hand-off errors, even if that introduces delays when it spans shifts. But not universally true across orgs, nor for incident types. Ex: For tricky & sensitive incidents that take 8-24 hours, the hospital results show longer shifts might make sense, so I'd want to see experiments before making assumptions!

Those facilities are also typically running three shifts, whereas you seem to be implying it is common for individuals to be working.. 24 hours a day, 7 days a week.

24/7 would usually be four shifts. The most common schedule is for each shift to run 12 hours, working three days one week and four the next, for a total of 84 hours per two weeks.

Three shifts works well for 24/5, each shift running eight hours a day.

Thanks!

We talk about humans NOT the Machines, Servers are 24/7 the admins are Not...i hope ;)