'Protection' might be the goal of physical fatigue, but it doesn't work for intellectual effort - what are you being 'protected from breaking' by not being able to write another line of code? Carpal tunnel? In that case, it looks more like it's about conserving energy or rotating to another task after having spent so much time on one task: "A Meta-Analysis of Blood Glucose Effects on Human Decision Making" http://www…
I find myself consistently productive over long spans without a burnout effect when I am sleeping at consistent hours, and working for consistent hours a day. When I overwork my productivity becomes inconsistent so I stopped doing that. I learnt it the hard way that late night coding is a short-term investment with negative return in the long run.
My personal theory is that our brains like consistency and adapt/tune to it over time. Just like when you jog every day, if you run for too long one day and too short the other day it cannot adapt/tune itself to a semi-random pattern.