How much sleep is required for optimal energy and recovery? I've heard 8 hours for people over the teenage years, i've heard 9 or more for teenagers. i've heard more than 9 is bad for your back. Is there such a thing as too much sleep , say 12 hours? Is this detrimental or benificial or neither? I don't know if there is a post with this as i've scanned around but if there is i'd appreciate a reply anyway, thanks! How about when you SD , how much sleep should you get?