I really hate having to make reservations in advance, because it forces me to be at a certain place on a certain date. On our trip to California and back in 2014, I had no pre-reserved camp sites. What we would do is when I knew we would be at a certain place on a certain date, usually a day or two before, my wife would call ahead and make a reservation. Of course it was a little easier to do that because we were ahead of the seasonal rush of campers. We left home in Virginia in mid February.
Unfortunately, on this year's trip I couldn't wait. I had to make reservations for Grand Tetons, Yellowstone, and Custer State Park in SD way ahead of time. It would be as bad if those three places were the 1st places we'd be visiting. Again, unfortunately, those 3 places are in the middle of our planned trip.