I've been in touch before, and found it to be a highly valuable exchange. I was just reading your post titled 'Watching the Lightning' and had a couple of questions, if you don't mind?
Firstly, do you find 4-7 hours sleep per night sustainable? I note the post was written a few months ago so I imagine this has been enough time to measure the success of getting aforementioned amount of sleep. I've tried to limit myself to 6 hours sleep a night, but found it a struggle after 2 or 3 days. I plan to push through the struggle as I imagine it will become easier after time, which leads me to my second question: what steps did you take when planning to reduce your time spent sleeping?
I have my highest performance levels overall when I'm average 7.5 hours per night. But often I get there in a funny way - a mix of 4 hour nights and 12+ hour nights. Beyond that, I think napping is valuable, diet/exercise/health is extremely important if you want to do it, consistency is important, and also getting high quality sleep in general.
I've recently come of the opinion that most people get very little really good sleep - too much artificial light, not enough exercise, bad diets, stimulant usage (caffeine...), inconsistent schedules, and so on. I think it'd be possible to run at the 4-6 hour sleep range with maybe a 30-120 minute nap each day, but you'd need to be near perfect across the board on all the good sleep elements with serious discipline about consistent schedule, total darkness and minimal artificial light before you're going to sleep, regular exercise, a perfect diet, maybe quit caffeine entirely?, and similar.