Keep in mind what type of Century Ride you are doing. Most around me are not races. Even the ones that do have timekeeping are not intended to be a race. Just enjoy it. If it takes you seven hours, eight hours or to the next morning to complete it, no one will think bad of you. In fact you have bragging rights that you kept the determination to the finish.
Your overall time can be shortened considerably by just keeping your time at rest stops to a minimum. Though you miss out on a lot of the social that way. I myself don't stay long because it's hard for me to get going again after more than a five or ten minute stop. And perhaps I'm just not a very social person.