I'm 77. Numbers are pretty irrelevant given all the variables. Things like terrain, wind, traffic, etc. But, my STRAVA history shows me what I did on a specific route on a specific date over the years. I will look back to see how I've done today compared to this time in past years. Even that's sketchy. On my favorite local roads over say 15 miles with 60 ft/mi of climbing I'm still in the 14-15 mph range when I have decent fitness. Gone are the days of doing my flat 1 mi STRAVA segment at 25 mph. hit that mark about 3 yrs ago. Haven't come close since.