For longevity and anti-aging, it is important to get enough sleep, and I think that 7-8 hours is about what is recommended. Your body can’t even start healing and restoration until it is done with digestion, so the earlier that you eat your OMAD meal, the sooner your body can finish he digestive process at night, and begin work on regenerating your body.
At night is when we go into autophagy, and that is when our body cleans out the old and damaged cells and builds new ones, so it is important to get enough sleep for the body to do its job.
That being said, some people seem to need more sleep than other people, so I don’t think that there is a hard and fast rule for how much sleep is necessary.