Have to chime in here as I come from a country that an ultra race we have is what defines the general publics view of what a runner is and that's the 56mile Comrades Marathon.(Google it for those who don't know)
The first question you get asked here by the general public if you tell them you run is Have you done the Comrades Marathon.
I have been luckily to associate with the best that have run this race and discussed all topics and can assure you what Krupicka does is common and would probably do ok at Comrades but just lacks a bit of basic speed ie sub 2hr16 marathon.Vladimir Kotov ran 1030km for the month of April prior to the race in May of 2000 and ran 5hr25min for the course at age 45.Michael Wardian who is also hardcore has run this race.Not to sure about the USA ultra scene but here or ultra elites run 2x44mile training runs at 6min22sec per mile and log high mileage as the norm and there is no taper only easy running close to race day