It's a tricky question, indeed. On one primary flat loop I ride, there are at least 15 intersections which theoretically or actually require a stop (or a significant slowdown) in the first half hour or so of riding. This is on a rec trail so there are also plenty of stops and slows for errant pedestrians who just have no idea what they're doing in addition to the intersections.

These groups are often walking 6 abreast covering the entire trail in both directions. Sometimes, joggers will just jump out of the bushes in either direction. Sometimes, cyclists will just come to a complete stop with no warning and u turn without looking back.

So, at least 30 stops/slows on a round trip ride of an hour. It could very well be 40 or more including all of the users doing whatever it is they're doing.

So, I don't know how to factor all of this in, except to assume that my actual average is much higher than what the computer indicates. Longer rides are generally better but overall I don't ride longer than 2-3 hours at this point on any given ride.