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Most of the data on sleep comes from the data obtained from the population based sleep studies . While this fits the majority of the population in around 10-15% of individuals this data might not be accurate.
Please allow me to quote from my reference material

"It is difficult to determine what constitutes a normal quantity of sleep for a given individual. One approach involves determining how long a patient would sleep if left to awaken spontaneously. An alternative approach involves determining how alert the patient feels after different durations of sleep. Alertness is normal if the patient wakes feeling refreshed and is capable of moving through the day feeling alert without effort, even when placed in boring or monotonous situations. This sense of easy alertness should be distinguished from alertness that exists when the individual feels pressure, since the latter may persist despite sleep deprivation.

Once the normal quantity of sleep for an individual (ie, the nightly sleep quota) has been determined, the sleep deficit can be estimated as illustrated by the following example. If a person who has a nightly sleep quota of eight hours sleeps only six hours, there is a two hour sleep deficit. That sleep deficit is carried over to the next day. A 14 hour sleep debt will accrue after seven days if two hours of sleep are lost nightly, which is nearly equivalent of two full nights without sleep."

- So basically what you are currently doing is right
- Do remember there is lot individual variation. I sleep 4-5 hours in the night, and almost never sleep in the morning. (without any cognitive or functional impairment )
-Timing of the day - There is no comprehensive data on this. Most preferred time seems afternoon. But whenever you feel sleepy is the best time !

Please note, if you are feeling sleepy easily in the day time, feeling tired, poor mood, irritability, low energy, decreased libido, poor judgment, inattention it is possible that your sleep quality or quantity is not good and it is time for revaluation.

Hope this helps
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Thank you