Have you ever watched any 24 hour racing events? Drivers do not race 24 hours alone. They do it in teams with each member taking 3-4 hours of racing at a time.
If you can find me a link to any 24 hour race that is driven by a single driver for the whole race I will consider your opinion valid.
http://en.wikipedia.org/wiki/Luigi_Chinetti
Luigi Chinetti was the closest I could find, giving up the car for only the final 20 minutes of the race. If you don't know the name, follow the link and read the story. This man is perhaps one of the most under-rated men in all of motorsport history. Absolute legend!
On topic, I have a daughter, and don't have a dedicated TV for the PS3. Regardless of where I go, someone will want the TV I'm using, and as per our family agreement (they can watch whatever so long as I can watch F1, Top Gear, and Colorado Avalanche/ Stanley Cup hockey), they can have it. I usually play when they're asleep, so I'm not disturbing anyone, and I don't have to worry about them distracting me from the game.
The only way I could complete a 24 hour race solo is to rent a hotel, and schedule a few days off of work. While this does sound like a wonderful idea, the reality is that the novelty would wear off after 4-6 hours, and it would start to become a chore. I'm working with a few friends to schedule a time when we all can tag-team an enduro, but all of our schedules vary so widely, that it's rare for us to even get a few hours together, let alone 24.
Then there's the fact that GT5 has two 24 hour enduros. Problems listed above X2.
Without the aforementioned family, I'd definitely complete both enduros, and I'd enjoy the delerium from the lack of sleep. But there's absolutely no way in hell I'd trade an enduro or two for time with my family.
Now, if GT5 wants to pay child support and alimony.....