Did an hour and a half (30+ miles) on this little bitty loop of 1.05 miles on this ride:
www.strava.com/activities/990631577/
I've actually done 40 miles on that loop before joining Strava (so I didn't record it). Those rides weren't as boring as it seems like they'd be because of focusing to keep 20 mph the whole time.
Here's a longer ride (with a few unplanned stops for chain trouble) on a more reasonable 8.73-mile loop - but it's still a fair number of loops:
www.strava.com/activities/1767453425