I'm hibernating like a bear at the moment and struggle if I don't get my 9. Really can't deal with cold weather and working evenings at the moment (need a daytime job more than anything else).
Usually need at least 7 to function properly though, any less and I am back to napping or gibbering like an idiot in the corner. Has to also be littered with one sleep a week where I get about 3 hours, usually based on really high alcohol intake or a criminal lack of exercise.