The mental aspect caused more anxiety than it was worth. The advice here about building base miles should be taken as gospel. Everyone in the group has at least 1000 miles in their legs this season with several 75 mile rides so this wasn't a huge leap in terms of miles, just a progression. We were very good about hydration and gels every hour, deli stops were for fruit and fluids, then we moved on. Stops were longer than we would have liked but we were 8 strong and waiting on line to purchase goods took more time than expected. Five of us had never gone 100 miles so we were concerned but the training really paid off.