It is not sustained/sustainable. I worked 100 hour weeks too, but then it took like a month to recover and during that time I could not properly work even 50 hours on my main job.
Agriculture is historically seasonal: you work a lot during some times, but the rest of the time you do completely nothing on the agriculture front. Not a luxury at most modern workplaces.
I do not know what you mean. What I described with regards to agriculture is how it worked historically with communities growing stuff for themselves or to sell at a local market. I encountered leftovers of that personally growing up. People could work hard in planting/harvest times during summer and in winter do mostly nothing except maintenance and such. I am not talking about commercial industries which may well be working people to the bone unsustainably (and illegally, if it was a developed country) with 12+ hour shifts. Barely a worthy example.
It's not all rare for certain workers to to spend 14+ hour days, 7 days a week, for multiple weeks straight, without any breaks. And they do this every year, year after year. And they can still live to their 80s.
The claim that a long period of rest is always necessary in-between 100 hour work weeks is simply not true.
I've met at least 1 person capable of doing 'creative innovative mental work' on a similar basis. Making categorical claims over billions of adults is simply incorrect.
Agriculture is historically seasonal: you work a lot during some times, but the rest of the time you do completely nothing on the agriculture front. Not a luxury at most modern workplaces.