I think both of you are correct: 1. I've also been it a hyper-focused state where I was so intent on what I was working on I would spend basically all my time

I think both of you are correct: 1. I've also been it a hyper-focused state where I was so intent on what I was working on I would spend basically all my time on that project without burning out. Like you, I haven't hit that focus state for a long time. 2. "18+ hour days", consecutively, is almost certainly an exaggeration, and this is where I agree with the parent commenter. For some reasons Americans (I am American) love talking about how much time they work and how little sleep they get. Realistically, very few people (except a small percentage of genetic outliers) can get by on sub-6 hours of sleep for long.