I rarely sleep more than six or seven hours, sometimes less. It was rather reassuring to read the often cited "Eight Hours sleep a night" is probably too long!
How Much Sleep Do You Really Need? - TIME
"Studies show that people who sleep between 6.5 hr. and 7.5 hr. a night, as they report, live the longest. And people who sleep 8 hr. or more, or less than 6.5 hr., they don't live quite as long. There is just as much risk associated with sleeping too long as with sleeping too short. The big surprise is that long sleep seems to start at 8 hr. Sleeping 8.5 hr. might really be a little worse than sleeping 5 hr"
