This is super interesting!
I've never heard of the Yana Frank system before but I completely understand how working within time frames like this is important and that you need to give yourself breaks. Giving yourself a time limit to complete work in can even be more inspiring and help with the creative process in a weird way.
That being said! Do you ever find that those time frames aren't enough? Do you ever find that just as you get into the swing of things your time is up and you need to do something else?