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.
@MHall It depends how much ultramarathon experience you have and how much cumulative base mileage you’ve built up over a lifetime. A common training strategy for ultras is back-to-back long runs (usually on the weekends). For instance, four hours on Saturday and 2-3 hours on Sunday, with an effort level you could sustain all day. In general, Adam’s time-on-feet recommendation is the best way to go. In ultra training, duration is more important than distance. Four hours on a rail trail or road makes for a faster pace than four hours on technical singletrack. It gets even more complicated when you add other variables like elevation change, weather, and high altitude. Best practice is to train on the same type of terrain as your goal race, if not on the course itself (i…e rolling asphalt for the Can Lake 50).
I strongly recommend you check out the book Training Essentials for Ultrarunning by Jason Koop. The author is a renowned coach who’s coached a number runners to the top of the ultrarunning ranks in the US. The book answers most, if not all of the questions you’ve been posting to this forum, has a ton of advice for beginner and intermediate ultrarunners, and gives a thorough explanation on how to create your own training plan for a goal race. Two years ago I used his method to make my own plan and ended up with the best race of my life at the Beast of Burden Winter 50-mile.