This technique makes perfect sense. It isn't so much 'rest as much as you play', but do rest when you suddenly start feeling fatigue set in (which is hopefully in advance of any subjective sensation of pain as pain ALWAYS trumps fatigue).
In playing just at 10-15 minute salvos, fatigue will in all high likelihood be completely prevented (assuming one is not holding out double high Cs for 10 bars at a time with just enough time to breath to do it again, and keep doing it for 10 minutes... and my guess is in this situation fatigue would not be as worrisome as initiating the phrase "Maynard, Maynard [read Annie, Annie] are you alright?.. at which point CPR is started.)
Maynard's technique as you noted is perfect, and now I understand how he could get demonstrate so much endurance with range out of practicing by never letting his muscle fatigue with this practice ethic.
Thanks much for sharing this technique.