The majority of the race is all in your head. Remember, you can rest when you're dead!
I did this race a few years ago, and my training regimen involved three rides a week, Mon, Wed, and Fri. Two of those rides I spent riding up and down Lookout Mountain, endlessly, with a backpack full of dictionaries.
The third ride was a looong ride--I think I started at 5 hours of trail riding, and worked up to 8 or 9. Then I did a road century or two thrown in during the summer to get the miles on. Oh, and as for the Lookout climbs, I think I started by riding from Denver (downtown area) out to Golden, and up and down Lookout merely once. I worked up to doing the same ride, and then climbing it four or five times in a row. Yes, it DID become psychological drudgery! I rode sections of the course beforehand, too, but not the whole course. I did the major sections--the powerline a coupla times, and then the Columbine Mine climb a few times.
I think it's really important not to overtrain for it, as many people overenthusiastically do. And pick your fuel early on, and train w/ it. I think I did Gu, water, and Cytomax, with turkey sandwiches thrown in.
It was a grueling, though fun, race! A little over the top. Chlouber's spaghetti dinner the night before was nice, though, and seeing that guy who wins every year was nutty.
With my very unscientific training program, I finished in 10 hrs, 50 min. Not fabulous, but respectable.
You can definitely finish it, if you have the right mindset, if you don't overtrain, and if you tell absolutely EVERYONE you know that you're doing it, so you CAN'T drop out for fear of being labeled a quitter. You did miss the deadline for this summer, though.
Next year, my friend, next year.