There seems to be a limit of 4 hours for working at maximum intellectual intensity per day.
The book "daily rituals" about highly successful creative people found few worked much more than 4 hours a day at their thing. They did do more hours but that was routine work.
Also there was a famous study of budding concert violinists which found that those who made it practised hard for 4.5 hours a day. They pushed to 4.5 hours by having a nap at lunchtime.
I have tested this myself and it seems to be true. Beyond 4.5 hours I burn out.
If you can do 4.5 hours a day of really hard intellectual work you will blow away the competition. So I suggest to people to focus on getting the 4.5 hours out each day.
* You cannot carry forward to any great extent. Use your 4 hours or lose it.
* Have a nap at lunchtime to push out an extra half an hour
* Usual hygiene factors apply - nutrient rich diet, exercise (small amounts of intense exercise, considerable walking / light aerobic), ample sleep.
* Most people find that the 4 hours is best scheduled for early i the day.
* Having a strong daily schedule really helps.
* You have to be completely hard core about the 4 hours. Let nothing get in the way of it.
I am looking for exceptions. I foun
d 3 possibles/ Proust, took caffeine tablets, died at 52. Erdos, took amphetamines, died at 80 ish. Possibly Richard Stallman who is a fanatic and burned out as a programmer mainly for phyisical reasons also it looks like he has the beetus.