I think sleep and mindfulness / productivity are influenced by long term patterns more than just day to day. If I get a good 7-8 hours of sleep for a while, but only 4-5 one night, I'm usually ok, but a week of 5-6 hours takes its toll.
There's also a lot of individual variation, though.
Also, It's not unusual for posts on the new page to fly by without many comments, particularly depending on time of day. (I'm a bit disappointed that nobody has noticed this one (http://news.ycombinator.com/item?id=1834864).)
"There's also a lot of individual variation, though."
Bingo. I need 9-10 hours. Sometimes I sleep 11 hours. And I never feel groggy after getting that much sleep, as some people do, nor do I just lay around in bed. I literally sleep 10 hours straight. I only got 4-5 a night during undergrad, and it took a severe toll. Speaking of undergrad, I knew a guy who had to get 13-14 hours/day, but he had some sleep disorder. Still, he had enough time to study and graduate with a great GPA, was very in shape, played hockey, and was a nice guy. I think a lot of people who think they'll be more successful at 4-5 hours/day are just less efficient and have a distorted view of what their "successful" role models do (i.e. they think their role models must not sleep a lot, therefore if they don't sleep/do work more, they'll also be successful). Just what I've seen in my personal experience though, I don't mean to impose this as a general fact.
There's also a lot of individual variation, though.
Also, It's not unusual for posts on the new page to fly by without many comments, particularly depending on time of day. (I'm a bit disappointed that nobody has noticed this one (http://news.ycombinator.com/item?id=1834864).)