Makes me wonder how so many people adapt to such endurance.
I've been racing 12hr and 24hr events on and off for the last 15 years, Mountian Mayhem and Bontrager (now Pivot) 24/12 mostly.
I've done a pretty even split of team and solo events and I love both ways fo doing it. I enjoy solo in a different way though, it's very much an endurance race and as much mental as physical, I've never quite managed to break into the top 10 when riding solo but have a had a couple of 11th and 13th place results at 24/12 and the placings from 4th-15th are normally quite close, but the guys who go for the win are on another level completely!
Last year I went back to team racing with some friends and we managed 3rd in the 24hr Mens, mostly because we are more stubborn than some others! The weather was atrocious and we jumped about 3 or 4 places overnight as some of the other teams pulled out where as we just kept on going, and going, and going...
Once you're fairly used to long rides it's the 16hr point that things start getting tricky IME. A 12hr ride is just a long ride, a 12hr race is hard work, but just an extension of that, creeping beyond to 14-16hrs is where you tend to be at the limit of normal endurance and also the point at which you're struggling to get fuel back in and you want to sleep so its a real challenge, once you've broken through that barrier and made it to 18-20hrs though your body kind of gets the message that you're not stopping and it's often back on the gas with a 2nd (or 3rd!) wind to the finish!
They are however excellent fun and I can heartily recommend having a go, a small team for a 12hr is a good way to start, or pairs, pairs are good, but hard!