Everyone has a different sleep pattern, 7/8 hours is said to be the norm but a lot of people sleep 5/6 hours without any problems. If you feel really tired you could always have the odd early night. As you get older you seem to sleep less at night, but doze off during the daytime. But if you are getting headaches, are you reading or computing for a long time each night, getting eye strain, do you drink alcohol before bedtime, are your pillows comfortable etc. I'd see your GP about a blood pressure check or health problems.