I seem to recall that what was more important than the amount of time spent studying, was that the students were engaging in deliberate practice; they were putt

I seem to recall that what was more important than the amount of time spent studying, was that the students were engaging in deliberate practice; they were putting in focused work intended to extend the boundaries of their skills. I think the analogy here would be that three hours of focused work (door closed, phone turned off, no checking email, no interruptions unless the building is on fire or someone is dying) would produce more, better quality results than 8 (or more) hours of work broken up by dozens of interruptions.