I get appoximate 6 to 7 hours off sleep a day.. I find if I sleep for more than that my back hurts...
I usually take around 8 hours of sleep which is enough for the human brain to function properly. Too much sleeping would just make my body hurt!
Whenever it's exams I'd not sleep at all, or less than 4 hours. Prefer 8-9 hours sleep. But average is about 5 hours..... Hm, doesnt sound healthy at all, I'm afraid...
I have been getting around 8 hrs a day in general but when I have to study for a test then I get about 6 hrs since I do my studying at last moment.