In reply to wbo:
Fair question. Maybe setup a ledge, ab off, rest, then climb back up to it, rest, and then go for the summit? David seemed unprepared for a high bivi, when Conrad seemed up for it but then agreed to go down. Davids third attempt he had a tent and set up camp high on the ridge, is that too high to have a rest day without o2? Otherwise was wondering why he didn't rest, go up to the summit without his heavy pack and then go back down to his high camp before descending.
Anyway, it's all speculation high above my pay grade.