I am no expert, and I know others will chime in here. But, here are a few questions that pop to mind.
How many years have you been riding? Have you done centuries before?
How hard is this century? Lots of intensity built into the terrain (hills, area known for headwinds, temps that will be difficult for you), or pretty gentle?
If you didn't bike all winter...did you keep working out aerobically doing something else, like in the gym? Were you a regular cross country skier who put in 3 hours of aerobic work on weekends, etc?
Just some thoughts!
"The best rides are the ones where you bite off much more than you can chew, and live through it." ~ Doug Bradbury