but is 8-10 hours of solid work really the goal? Or... condensing down the 2-3 hours of real work in to, say, 3 hours, then using the rest of the time in some other capacity?
"A good traveler has no fixed plans, and is not intent on arriving."
I'm optimizing and seeing what happens. If I hit a stubborn limit, and nothing works to break it, I'll accept it. But at least I'll know what's going on, and as you say, I may plan better the rest of my day.