How hilly is the century? For me, I can gut out a relatively flat ride for which I'm undertained, but hills add another dimension of fatigue and pain that can be difficult to overcome with less than adequate training.

But I otherwise agree with Tri girl's suggestion. If you can get a long ride in next weekend and feel okay, go for it. The pace in which you did the 54 miler in suggests to me that you've got it in you. Just go out pretty easy, drink and eat enough, stretch a bit at the stops, and you should be okay. Of course, weather could play a factor, too, so if it's windy, just play it by ear.