In the podcast between Spencer Greenberg and Buck Shlegeris, Taking pleasure in being wrong, Buck says:
I think that when you are learning subjects something that you should really be taken your eye out for is the simplest question in the field that you don't know the answer to.
I think a lot of the time people try to learn physics or something and their approach is as quickly as possible to answer hard questions about complicated subjects. And I think that's what I thought was cool when I was younger. They delighted at questions that were at the limit of fanciness that they could possibly answer and it feels to me now that it is a lot more productive to seek out questions that are as simple sounding as possible while still being really hard to answer. Or that still demonstrate that there's something you don't understand about the subject.
[...]
It seems like we should be seeking out these most basic questions in the hope of finding holes in the foundation of our knowledge.
If we apply that approach to applied rationality, what questions do you have that seem to be simple but where you don't know the answer?
(Apologies in advance if any/all of this is obvious to you)
Too much sleep is bad, too little sleep is bad. Sleep needs vary per person and throughout life but generally >6 hours, <9 hours is the range.
You don't really sleep in 'hours', you sleep in cycles (https://en.wikipedia.org/wiki/Sleep_cycle) so measuring based on hours doesn't work so much.
If you wake up naturally sometime in that 6-9 hour window, and you sleep deeply through the night (smartwatches are good at measuring this), you're probably getting enough sleep.
If you have reason to be concerned about your sleep, consider getting a sleep study done.
The benefits of more sleep are less relevant than the downsides of not enough sleep - chronic sleep deprivation is very, very bad.
If your mattress is noticeably uncomfortable, it sounds like you need a new mattress :)