Yes, man management in those operations has to be good, and his must be outstanding. Delegation is a skill in itself, not always recognised. He has been so successful for so long, it is no accident.
The 'mental health' aspect referred to by Turny I found interesting however...do not many trainers do similar, given the limitations/advantages of their location?
I know many who will allow their horses paddock time - a weekend away from the stable routine, or similar - post-race, and where farms or agistment facilities are reasonably close, send their horses for a break, regularly. One comment attributed to K Myers, after a racemeeting and long drive home, was ' salad tonight, fellas ' and into one of his many good paddocks they went, to stay on good pasture for as long as the boss deemed suitable.
Chris Waller, as a Kiwi from a fairly rural area, would be only too aware of the value of such management - but certainly isn't the only one to be so.