I’ve built in 7 towns (8 if you include Rouen) for this itinerary, with a total round-trip drive of 158 miles.
Now, don’t panic — this is meant to be a full day tour, and you don’t have to visit every town. For example, you can shorten the trip by about 40 miles if you skip Gerberoy. Also, while there are 1 or 2 towns that might require an hour or so, a few are very small and you probably will decide to just drive through and grab the ambiance on the fly. I tried to cover all the towns worth visiting, but where you stop is your choice. Usually I follow these itineraries as is but I’m very selective as to where I stop.
The easiest way to get the trip done is by GPS — going by written directions and road signs is a hassle, and you’re likely to spend some hours trying to figure out where you are, how you got there, and how do you get out of there. With a GPS, you can plug in each town before you leave, save it, and go to your saved destinations when you’re ready to move on. Easy as pie.