I need to be at Glacier in late June and many be limited on when I can get away so I may have to do the 2200 miles in three days as there not much I need to see again on the first two days. I think the Bad Lands are well named BUT I like places with trees. Later in the summer I plan on being at the Tetons and Ystone again this summer without reservations for the 5th+ time. My point is I would not make any reservations assuming you have a generator and can boondock for several days. Once you make a reservation then you loose flexibility as you make like the BAD Lands and want to spend more time there.