I remember a study that showed that people who get less or more than 7h of sleep die sooner (the larger the deviation, the sooner they die). However, I don't think this study normalized against factors that are correlated with excessive/deprived sleep.

I currently sleep 12h a day and I'm okay with it because I value my sleep time more than daily time unlike this person. If I sleep less than 12h, I notice that I'm tired during the day. Some people say that they feel lazy and cognitively impaired if they sleep 12h, but this is not the case with me.

I have seen both the 7h recommendation as well as the "sleep as much as you need to" recommendation. Which one is the best one in my situation? This question has previously been asked when the original poster asked if his 5h are enough. The top rated answerer was skeptical, and quoted the NIH: "Some people appear to need only about 7 hours to avoid problem sleepiness, whereas others need 9 or more hours of sleep". My main question is with respect to the "or more" in the NIH quote: Is 12h of sleep still reasonable/healthy?