You’ll get it. I’ve run two 100s and I’m running my third in a few weeks. The suffering really begins after 100K or so. It’s a long time on your feet.

If that doesn’t do it for you, let me recommend one of these options:

- The Last Annual Vol State 500K. https://ultrasignup.com/register.aspx?did=34762

- The Quintuple Anvil Triathlon. https://www.nytimes.com/2016/11/06/sports/virginia-quintuple...

You might also want to explore timed races where you run as far as you can on a loop course in 6 hr, 12 hr, 24 hr or 48 hr.

And if after all that you still haven’t found what you’re looking for, I can only recommend the Self-Transcendence 3100 mile race. http://www.3100.ws/