It is interesting to see the spurts and rests quantified. I suspect that the 52–17 blocks may differ by individual.
I finished more than 100% of my work in an 8-hour day and never had a project fail. Everything I did moved my projects forward, one software project and the other training new programmers. I never had a late project.
My daily goal was to work 8 hours, no more. I would in an emergency, but that meant that somebody screwed up.
One of my most productive periods was overnight. I went home, gave my brain a problem, read sci-fi, and woke up the next morning with the solution.
One manager took advantage of that by giving me the horrible problem before I went home instead of waiting until the next morning like he would everyone else.