Why stop at 8?
I function best with 8-10 hours of sleep (which usually means about 12 hours in bed, though less so now I'm not being woken by my bladder every couple of hours). I usually get by with a few nights of 6 or so, but have to make up the deficit at some point, otherwise my brain stops working properly. Nights with no sleep (either deliberately, or due to illness/insomnia) are doable, but I'll be unsafe around the 10am lull, and will need to catch up the following night.
I'm finding it harder as I get older. Unless actually exhausted, my body still doesn't want to sleep until at least 1am (and going to bed earlier just means I thrash around, get less comfortable and fall asleep later), but has decided that being awake at 6am is a good idea. I either spend a couple of hours reading to get through it and go back to sleep for a bit, or get up and spend the rest of the morning in a zombie stupor - depending on whether physical presence or mental performance is more important for the task in hand.
It's harder in the summer. I try to be as nocturnal as possible to avoid the morning pollen peak, but waking up at 6am and having the change-in-blood-pressure sneezing fit and optional nosebleed, then the east-facing bedroom getting stupidly hot isn't helpful with that.
Barakta needs more sleep than I do, which isn't surprising given that she had the additional demands of dodgy balance and intense concentration to hear. She'll not infrequently come home and crash out for a few hours, and spends most of her days off sleeping until the afternoon.