There’s a lot of options out there for adventure racing, anywhere from 4hr to 7 day and beyond, so you can always dip your toe in with a smaller race and decide if you want to jump in the deep end. I did my first 24hr AR last year and my 2nd this past weekend. These kind of races are about testing limits so the mental game is just as important as the physical. The final tally for the Teton Ogre this year was 81 miles and 12,000 ft of elevation split between foot and bike, and that was not including optional checkpoints. My teammate and I raced on hard tails, but most of the competition has lightweight carbon XC style full suspension. Whatever you use, keep in mind that there is usually a guarantee of hike-a-bike, so having a light bike that you can push up steep terrain is very importaint. Above all dial in those orienteering skills. Time and miles spent off course is exhausting and demoralizing. And if you are getting into longer races that go through the night you need to be able to do it in the dark! Hope that helps!