I am asking whether adults, especially in circumstances like a monastery or Zen center, can become able long-term to sleep only about 4 to 5 hours a night? So, that would mean: no children to care for, no heavy labor, lots of time spent meditating and doing other things that the body would find restful and undemanding...
Can the mind get along on much less hours of sleep than the usual adult? I am not asking about the absolute numbers, only if it can be reduced and sustained over years, or permanently?