HOW MANY HOURS DO YOU SLEEP PER DAY?

You should sleep as much as you can.
You'll never know when you get into a situation when for some reason you won't be able to sleep deeply.

Just think about it: a few million years of evolution lead us here, and we need to spend 1/3 of our life in a completely paralyzed, vulnerable state to survive.
Do you think it's a coincidence? There's a really good reason for it, so sleep as much as you can.