Gerry Lindgren supposedly had monstrous (north of 200 mpw) in his career. It seems that for many a gradual buildup of up to 5000-6000 mi per year is a good recipe for success, not taking into account an individual's particular work schedule, body fatigue, stress level, sleep, etc.
Anton Krupicka as noted, had brief success logging lots of 200mi weeks - and many of those were on mountain trails which might equate to a bit more. While he has experienced chronic injuries, for the last number of years, that can also be b/c he never took a break from running during the year. Now, out of necessity, he hikes, rock climbs, and cycles.
Other successful ultrarunners who log big mileage are Sabrina Little (AR for 24hrs) who will log up to 200 mpw during serious training (in addition to gym time/ weight training), and Alyson Venti who will log up to 300 mpw during serious training (3rd fastest US female 100mi set at Keys 100, 2 years ago - also ran under CR at Spartathlon this year, though was beaten by teammate Katalin Nagy). Both of these women are still young and time will tell if their recipes hold up. Of course each is an experiment of one.
One would have a tough time justifying logging that miles in the name of training. Highly successful road ultrarunners often have similar training to marathoners. Yiannis Kouros was reputed not to train more than 80 mpw in his prime. Even if one were to guess that warmup and cool down miles weren't included, he wasn't logging more than 100 mpw. I can cite a laundry list of others, but for most folks, 140mpw is probably the very most one could benefit from in training, and even that would be too much for many.
Now, if you enjoy logging more than that, great, but it ain't necessarily "training" at that point.