According to Mathew Walker, a neuroscientist who specialises in sleep and is considered the world's leading expert, it's 8 hours, with 8 hours 30 minutes being the absolute max.
Definitely a truism. Just like the people who suffer the most with mental health problems, or the combat vets who saw the most horrific shit, are always the ones to never talk about it.
My counter sarcasm to the Dane's original sarcasm triggered you?! That's amazing :D