We never leave the driveway without reservations. Maybe it's just a security thing, especially with me. When planning a long trip, I use MapQuest, know that we want to do about 300 miles per day, so I start looking online for "campgrounds in ___ area". If you're going across I-40 from OKC to Amarillo there isn't a lot and the campground we stayed at in Amarillo was great, but not many others that were convenient. On a trip to San Antonio area, the pictures online of a small campground were very nice, but up close not so much. I just called after we passed it and told them we were way ahead of schedule and needed to cancel for that night since we were driving further. No problem as long as you call by about 6:00. Heading to the UP of MI, reservations all the way. I just don't like having to be ready to park it for the evening, fix some dinner and relax with something cool rather than trying to find something that is acceptable.
We even have reservations for our local campgrounds because we have sites we prefer over some others....never fails that it will be taken if we didn't reserve.
Sort of a moot point for us now as Rocky is going with his new dad on Monday and we'll be trailerless, probably permanently. Darn!, going to miss it terribly, but life changes come along and this will be better for our family.