In that case Jamie, listen to all three podcasts that I specifically linked to and decide for yourself and get back to us. There have only been two books I've been able to finish because they were too distressing, one was
The Gulag Archipelago about the Soviet Prison camp system by
Aleksandr Solzhenitsyn, the other was Matthew Walker's book,
Why We Sleep.
The evidence is overwhelming of the chronic effects of sleep deprivation. You will die of sleep deprivation long before you die of starvation. Without sleep you will be dead within weeks. Certain disease that result in chronic inability to sleep result in death within 18 months
Fatal Insomnia
The Guinness book of records no accepts sleep deprivation record attempts to heath concerns.
In answer to your question about a 40% payrise to do it 4 man crew, moot point, that has not been put on the table. Just the opposite, I've heard reports of the initial offer being between
-30% and -10% (yes, they are offering minus) to have the privilege of doing this flying. No thank you very much.
If, as you say you have had a career of longhaul, I challenge you to finish the Walker book, Why We Sleep and report back to us how it is all scare mongering.