> I don't believe it when research claims X because of personal experience.

That's a horrible way to look at any research conclusion. Have you considered you are possibly oversleeping? 7.5 hours might be a magic number (exactly 5 rem cycles) as opposed to 6.5 which will put you waking up in the middle of a rem cycle. Studies can be faulty for a whole bunch of reasons but dismissing a body of work because your little n=1 experiment didn't sync up with their conclusion is just willful ignorance.

I don't see how one can oversleep, if you don't need anymore sleep you just wake up, that's how it works.

First of all, that has nothing to do with the point I made in my last comment; which is you can't dismiss peer-reviewed research based on personal experience.

Second, that is not how it works. There are varying levels of sleep. Some better than others. When your body doesn't need to go through rem sleep anymore it is sufficiently rested but that doesn't mean you feel like a ray of sunshine and immediately jump out of bed. There are other factors which make a person want to stay in bed longer than they should which leads to shitty non-rem sleep. Too much of this makes you feel groggy.

Have you talked to a doctor about that? Specifically an expert in respiratory issues might be able to help.

I have no trouble breathing whatsoever.

When you're awake? 'cause people who have sleep apnea don't usually have any trouble breathing whatsoever either. Use your phone to record a nights sleep, or at least SOME sleep, and you might hear: snoring, no breathing, sudden panicked gasping for breath, all without waking up. Or hopefully, just the snoring. Also, you were great in Sin City. :)

You can be completely fine while awake, but still have apnoea while asleep. If you are sleeping that much and not feeling refreshed, it definitely seems like something to get checked.

When i'm awake i don't either. But when asleep it turned out i was sometimes not breathing for up to a whole minute.

That's fucking terrifying.

Depends on how old you are, really. For a young guy like me it's no issue, i just didn't get much rest, since during the night my blood oxygen level was like that of an 80 year old. Once you're elderly though it can easily lead to an untimely demise.

Talk to a sleep specialist.

You may be suffering from any number of medical problems interfering with a good night's sleep.

Things like CPAP machines are transformative for sleep depth

10 to 12 sounds excessive. Sometimes I sleep 14+ hours a day. It's usually because of another problem, and oversleeping often drives a depressive state. Going a day without sleep, or getting 3 hours, usually makes me very hyper.

You should consider doing some research or consulting with a doctor.