I'm doing my first Century on Oct. 25th by myself, too. But then I always ride solo--my DH doesn't ride and there's no groups around me to train with or ride with. So, I'm on my own, as usual. The mileage isn't that much of a concern as is keeping my glucose levels up throughout (T2 diabetic). Which is way I'm glad though it's a supported Century--plenty of people around if I start to bonk.