How much sleep is needed for a 52 year old woman?

I read a great way to tell how much sleep you should get...

Evey night for a week, go to bed at a reasonable hour, get up when you usually do. Don't do anything unusual like staying out really late or drinking. Do this for a week and on a Saturday or day you don't have to work don't set the alarm. When you wake up naturally should tell you how much sleep your body requires.