I have been Strava-ing for over a year now, and have made several friends that I have been following. I look at their 40-60 mile rides and see average speeds of 15-16-17mph, and I look at my 30-40 mile rides and see 11-12, and sometimes 13. Today I did a ride I have done several times and When I logged it into Strava saw an average speed of well over 14 MPH.
Disclamer-the last four miles were with a pretty stiff tailwind, but that doesn't diminish how I feel about it. Four miles averaging about 21 mph still made me want to let loose with a Tarzan yell.
In the last two months I have actually started concentrating on something resembling training, and have renewed focus on weight loss. I used to back off and cruise when the burn in my legs got uncomfortable. I'm learning to focus on cadence while working through the burn (Mind over Muscle) Long sections at 3-4% are now 14-15 mph. I focus on keeping my HR at 140-145, and its working at giving me a good balance of power and endurance.