If you're doing it to impress someone else, I guess you have to use their rules. If you're doing it for yourself and for your own fitness, use whatever you want, as long as you're being honest with yourself.
I did one a couple weeks ago, and had to stop to change a flat, refill water, and pee a couple times. For the sake of assessing my own fitness, I only really considered riding time, because all stops were necessary, and I feel like I could have done it faster, or at least just as fast if I hadn't had to stop at all. At least for me, my legs are worst off right after a stop when I get moving again. I'd love to ride six hours start to stop, but I'd need a friend to sacrifice an entire day to drive a support vehicle, and I'm not concerned enough to ask that of anybody.
If you think part of the skillset required to ride a fast century is being able to change a tube quickly, pee quickly, "hold it" for a long time, refill a bottle quickly, run stoplights without getting ticketed, take a fast dump, and eat without chewing too much, use overall time.
Last edited by Kind of Blued; 11-04-11 at 07:55 PM.