> working 80 hours a week outputs productivity somewhere between 1 to 2 times the productivity of 40 hours a week
Effort and energy spent will be somewhere between 1 to 2... but as soon as stress and exhaustion set in (which may happen fairly soon) you may find actual productivity tanking well below 1 and even into the negatives, due to all the mistakes and bad decisions you start making.
Take a delivery truck. Regular maintenance detects, and prevents breakdowns during deliveries. EG, oil changes, lubing, brake pad changes, etc.
Scheduled repairs are far cheaper, and take less time than unannounced repairs.
If the truck breaks down during deliveries, the repairs are still needed, may be more severe.
It also require loads of extra work, a replacement truck must show up and offload deliveries, a tow truck dispatched, someone had to organize this, customers upset and called, etc, etc.
As you say, humans are the same. Reduced sleep and leisure time (scheduled maintenance)?
Well, it's far more work to deal with in the long run. It takes more maintenance to recover from a lack of it.
This is, by the way, the vicious circle in which the Russian war effort in Ukraine is now.
The more tanks, trucks, fighter jets you lose, the more sorties/tasks the remaining fraction has to pull off. Which means more wear and tear, higher risk of failure.
Effort and energy spent will be somewhere between 1 to 2... but as soon as stress and exhaustion set in (which may happen fairly soon) you may find actual productivity tanking well below 1 and even into the negatives, due to all the mistakes and bad decisions you start making.