Importance of long unbroken Sleep

A long unbroken sleep is necessary because there are just ten minutes of the whole into which one enters into a true rest—a sort of Sachchidananda immobility of consciousness—and that it is which really restores the system. The rest of the time is spent first in travelling through various states of consciousness towards that and then coming out of it back towards the waking state. This fact of the ten minutes true rest has been noted by medical men, but of course they know nothing about Sachchidananda!

Ref : Letters on Yoga III