To run 100, you need to run. But not nearly as much as you think.
The LT100 is in August and I committed to doing it the previous October. My initial plan was to run at altitude on hills until the snow came. The. I would switch to skate skiing. I set an intermediate goal of Glide the Divide: a skate ski double marathon from Steamboat to Wyoming and back along the continental divide. However, after a few weeks of this plan, I was injured and not at all confident that I would get to the starting line, much less the finish line of the Leadville. In a typical year about 750 sign up for Leadville, 500 start and 250 finish. I've known a few of those runners who DNF - they were very fit, strong and ultimately humbled by the course. So I knew I could not take this lightly and expect to finish.
So I got help. Fortunately leaving in Boulder there are a lot of veterans who are happy to help. And I hired a coach who has been helping others train for Leadville for 20 years.
Lesson 1. To run 100, you run and not ski. In fact, you don't do anything but run. No biking, swimming etc.
Lesson 2. First master the distance, then add hills, then altitude.
Lesson 3. Do run walk patterns. Forget about your marathon training. Run .9 walk .1 from the first mile. Every workout. Even the short ones.
Lesson 4. Only push yourself twice a month.
Lesson 5. Split your week in two and balance the miles.