I participated in a metric century this weekend that covers parts of my daily routes. I averaged 16.1 (according the garmin) and was completely happy with the ride.
I did the whole thing solo, and stopped at the 46 mile pit stop to top off on water and grab a bite. That was the only stop I made. I found it funny at the end when I finished with the faster groups. They were obviously faster than I am. but they had to pass me 3 times since I didn't need to stop at every pit stop.
BTW. that's pretty much my usual average speed on a longer ride and I'm happy with that. I can do better on short days.