twocats It's not about taking breaks, it's about the physical limitation of the brain. If the human brain can only learn for 5 hours a day before it tops out, it doesn't matter if you're taking breaks or not, that extra 3 hours of practice is wasted time.
I have thought a lot about this particular thing. I do think that SOME people can benefit from practicing more than 5 hours a day. Brains are different, and while it's true that the AVERAGE brain would top out after 5 hours, I do think people who are intellectual giants often have some kind of neurodivergence that allows them to practice more hours while still being effective. For someone who does not have that kind of neurodivergence, it would be counterproductive to try to do so. This is NOT the average conservatory student, but if you told me Yuja Wang could do it, I would believe you.
This is similar to how certain people naturally don't have to sleep more than 4 or 5 hours a day. These are people on the tails of the bell curve. I have met some people like this. They don't try to sleep less, they just naturally don't feel like sleeping more than that and don't seem to suffer any loss of concentration or vitality from doing so.