We have been at it since June 2006. Try not to travel over 200 miles per day but sometime is necessary to go further in the north central part of the US because of lack of campgrounds. Nearly always lay over a day when mileage exceeds 200 mile.
Usually do not make reservations in advance unless there is only one campground in the area. The exception is over national holidays. But we do call ahead an hour or so before we get to the town we want to stop in and check availability.
We decide each year where we want to go then very roughly map out a route. Have always changed it because of illness or we just find other things we want to do or see inroute.
We usually have a definite time for 2 or 3 stops during the year then work our travel time in to corresponded to those stops. Example: The trip this year. Need to be in Saskatoon, SK on 16 Apr. Will spend a month then drive across Canada to arrive in Montreal on/about 15 Jun to meet my cousin. Then up the Labrador Hwy, across the ferry, and arrive in Twillingate, NL for their annual festival starting 20 Jul. Then back on Texas before Thanksgiving.
As you can see that leaves a lot of days unaccounted for in the planning, but it all works out. There will only be a couple of stops where reservations will be made in advance because of Canadian holidays. We have traveled like this for over 8 years without a problem getting a camp site in or around the area we want in.
I know many people are not comfortable traveling without reservations, and I have no problem with that. Everyone needs their own comfort zone. We just want more flexibility to change our minds and having confirmed reservations for most stops are not for us.
The website for my trip logs and photos for our travels to Alaska and Canada are in my signature.