I'm 60 and I don't use a speedometer. I know I've ridden at least 170,000 miles on road bikes and have no idea what my average speed is, or was, except when I come home and look at the clock. I usually ride with others or on known routes in the mountains with 100 feet of climbing per mile, or more.
Mountain riding = about 10 mph with food stops, etc.
Oh, a thick skin will help around here.