We have taken a couple of 7000-8000 mile trips since retiring. I make a plan, look at it frequently, then end up where we end up. We don't sweat it if we end up short of our planned campsite. We try to find local stuff to look at along the way. We have locations that we really want to see, but if we miss them, the world will still be spinning in the morning.
I like the idea of breaking the trip down into mini-trips. I never thought of it, but, that is what we do. I am now planning my next trip that includes the following NP's:Theodore Roosevelt, Glacier, Yellowstone, Tetons, Dinosaur, Arches, Canyonlands, Mesa Verde, Black Canyon of the Gunnison, Rocky Mtn, Devils Tower and the Black Hills area. We have no idea what the time frame will be.