I've worked intense 10-12hour workdays in the past for long periods of time (waves of 3mo), but they all had at least three of four things in common: Agency, Interesting, Interruption, Reward.
Agency is important to me -- am I bought into what I'm doing and understand the importance+urgency and get to direct the work -- or is someone up the chain jamming some feature down to check a box for their own personal reasons w/o good reason. This encompasses Respect -- where everyone understands the rationale and why some urgent deadline is present and people are not told to go on unknown journeys "just because" or "you dont understand"
Another is Reward. When working at a hedge fund, sometimes, things were not interesting but there was a clear reward I was psychologically aligned with the reward. Same when I was Founder/CTO -- there was a clear reward (not always monetary.)
I think when you hear 2hrs/3hrs/etc per day, often it is the fault of the organization for:
- Not having good business cases
- Thinking Engineers don't care about reasons for doing things
- Not providing distraction free blocks
- Not sufficiently sharing rewards with the company