Check
http://science.howstuffworks.com/sleep.htm
And
http://en.wikipedia.org/wiki/Sleep

Hi, Ihhai,
8 hours a day is the norm. It can vary somewhat, but the brain needs time to "unwind", recoop, and rest.
Jobs that require 10 or 12 hours a day "on the job", require more sleep time that normal 8 hours a day jobs.
Eventually, not getting enough sleep will result in being sleepy, not being able to "give all you can", and have you feeling "run down" all the time.

I read somewhere recently (cant remember where though), that the 8 hr rule of thumb norm is not necessarily accurate anymore, and rather, it is 9 hours a day of sleep that we need. Although, Id still take 8/day if I could get it.

Oh really? That's interesting! I still maintain it's highly individual. I couldn't sleep 9 hours unless I was sick or something. I automatically wake up after 7 hours, and I can't sleep in no matter how hard I try!

I agree, very individual. There are some that can function very well on 3 or 4 hours a night.

All depends on the person.
And probably the job too.

I agree.

It most likely depends on the individual as each person is indeed different.

I heard that doctors recommend between 6-8 hours, but it is not enough for me. I feel charged with 9 hours, but I am also afraid that it can be harmful.