I think I've figured out the common features of the best mountain ultrarunners.
a) they run consistent miles, day in, day out;
b) they run these miles on very steep terrain.
Think about it; Geoff Roes only started to churn out victories at every ultra-distance after moving to Juneau, Alaska, where the sea meets the mountains and the trails go straight up.
Anton Krupicka had, arguably, his best race season last year after completing his 100 summits of Green Mountain - he initially described the trails in Boulder as insanely steep.
In training for Hardrock, Dakota Jones has been basically post-holing up the huge mountains outside of Silverton, Colorado.
I always say this, but next week, when I (hopefully) can return to running, I think I'll quit my ridiculous touching-the-stove-to-see-if-it's-hot training method, and return to running for 1-1.5 hours every morning, with plenty of Cootha ascents on the Chapel Hill Road, Lookout, Reservoir and Kokoda trails (the steepest).