I just did the Death Ride over the weekend. What an adventure. It was the hardest century I'd done.
I didn't train as much as I should have -- about 500 miles during the prior three weeks -- but it was enough to ensure that I finished. It took about 11 hours (including rest/fueling times) to complete 129 miles and 16,000 feet of climbing.
I'd heard about this ride for a while and never thought I'd ever be ready. Well, at times, you just have to say: "What else do I have to do that Saturday?" So -- don't put anything off - just do it! You may surprise yourself.