A great ride and report. I don't have too much experience with centuries and I've never done one supported, but I can totally relate to the idea that strategy goes to hell when presented with the opportunity to draft with a fast group. It's just too much fun to be thinking about the consequences later in the ride.

Looking at my ride logs, I see that there's a tendency for the longer rides to actually also be among the faster. This is partly because the longer rides are out in rural areas with few stops, turns, and so on. And the slow parts have less influence when averaged over more miles. On a short ride in the city or suburbs, I have to spend a high proportion at 22 MPH if I"m going to average 18 MPH. On a long ride where there are 10 mile sections without a stop sign, I can average 18 MPH with most of my saddle time doing just 19-20 MPH (depending on wind, hills, etc.).