...could Noburi not train with Tsunade all day and then with the Sages at night? I can see Tsunade's training being long because it's a lot of theoretical, knowledge-based, and chakra bullshit, but the Sages' should be physical right? Can't be more than a few hours.
We learn TH for 12 hours a day, but I don't think we spend all that time with Haruhisa in direct lessons. Rather, I think some portion of those 12 hours are expected to be "homework", practicing what you've learned today and reviewing what you've learned so that it sinks in in time for your next lesson. These 12 hours are meant to represent a "full time" commitment, because the few hours left in the day are likely to be filled up by food and chores and such. You're saddled with enough work to monopolize your time without interfering with your ability to keep up your day-to-day life.
This is, as I understand it, also the model for learning Sealing and Summoning. Broadly speaking, it looks like the QMs model any "full time" learning experience as requiring a "full time" commitment, approximately 12 hours of your day, regardless of how much is spent in direct tutelage versus self-study. I figure the same will be true for both Tsunade and the Toad Sages. Tsunade because, as you said, it's all very theoretical, much like Sealing/Summoning/TH, but the Toad Sages aren't
just aiming to raise Noburi's Physique. Alertness, ninjutsu, any and all ninja skills they feel are relevant to making Noburi a summoner worthy of the Toads. Jiraiya, basically. They're teaching him how to be Jiraiya and he'll be learning and practicing everything that entails. I easily see them going "here's a fancy chakra manipulation, go practice it for the next few hours and make sure to have it mastered by tomorrow's session, we'll be using it to help you learn <mumble mumble>".
(And, while we don't typically run into "out of chakra" problems when studying any of the forementioned disciplines, even if the Toad Sages' training is heavily chakra-intensive it's
so not a problem for Noburi. So, so much not a problem for Noburi. That just leaves physical exertion and strain, but hey, there's plenty of stuff to learn and all day to learn it.)
In short, I find it really hard to imagine that Noburi can pull off both at once, unless he goes to Orochimaru and picks up that anti-sleep bioseal.