Anecdotes about how "hardcore" people are in this regard usually wind up being worthless. 9 times out of 10, when I ask someone about an "all-nighter" they just pulled, it turns out they actually stayed up until 4:30 and slept until 9.
I expect most people who talk about how they can stay locked in the zone for 8 hours, in reality take breaks for coffee, browse the internet, and break for lunch.
(There's nothing wrong with taking breaks!)
(1) Me. Just now.