Hadn't played in a while, so I decided to find a nice small paradise moon and see how long it would take to drive all the way around it in a Pilgrim exocraft. Answer was about 90 minutes, with relatively frequent stops to look around. Non-moon planets are much, much bigger though, so I'm guessing even a small one would take several hours.
Definitely strengthened my belief that (some) moons need water though, water just makes terrain so much more interesting. There's a wish for the Beyond update.