I also notice that the more complex a task is, the less hours of it I can do.
If I know what to write, and I just have to crunch out pretty straightforward code, I can do more hours (nowhere near 12 hours though, maybe 8 at best).
I can imagine the work your dad did, didn't include juggling a big complex system in his head, which seems to require a lot of mental energy.
That's basically also what Carmack states, that you can reach 12 hours if you plan your work to include some easier tasks for that day. But then again, I was never able to really apply that strategy.
I think it mostly takes mental energy to addapt to change. I think you can focus on a large complex mature codebase and make small improvements so long as you're not radically chaging everything. Maybe it comes down to synapses firing versus synapses rewiring but that's just a laymans guess.
If I know what to write, and I just have to crunch out pretty straightforward code, I can do more hours (nowhere near 12 hours though, maybe 8 at best).
I can imagine the work your dad did, didn't include juggling a big complex system in his head, which seems to require a lot of mental energy.
That's basically also what Carmack states, that you can reach 12 hours if you plan your work to include some easier tasks for that day. But then again, I was never able to really apply that strategy.
Thanks for you take on it! :)