I am 50 years old and have been cycling regularly (recreation only) for 3 or 4 years. I recently did a 50 mile ride with gorgeous weather and very moderate rolling hills and finished at an average pace of 16.1 and was absolutely thrilled. I did another 50 mile ride a few days ago which was hillier and hotter and finished at 14.9, and felt disappointed in myself, which is ridiculous, but there it is
It is so easy to get caught up in comparison to the point that riding is no longer fun, but I agree that it is very motivating! I mostly just try to keep up with the riders I'm with and have found that my pace has increased (slowly) over time - especially since the other riders are usually a little faster and I have to push myself.
Grits
2010 Trek 5.2 Madone WSD, SI Diva Gel Flow
2002 Terry Classic, Terry Liberator