This average speed for an hour changes 2-3 mph depending on how relaxed I am in the parking lots before and after. Cropping it is like cheating - just crop the fastest hour then but then it's not an "average one hour ride", it's the fastest of a one hour ride. So for me, the metric doesn't mean much.
If I keep track of anything, it's how long does it take me to get to the store, the pharmacy, etc. That makes sense to know, but it's surely not a performance measure.