People like @Petorius and @RichHeffron who have done ultras likely know more about it than I do, since most of my training and coaching is at distances from the 1 mile to the marathon. That said, if your goal is to do stage races or other events where you’re spending a lot of time on your feet, I’d think that multiple long runs at easy paces would be essential.
I’ve been thinking more about time on feet recently, since someone who runs a marathon in 5 hours, for instance, is going a lot slower than someone who runs it in 3 hours, but is putting a whole lot more (or at least different) stress on their body. Lots more steps. Particularly when the goal isn’t to run as fast as possible, that’s going to require some changes to training.