While we don't make res for every night if we're traveling around during one of our 1-2 week trips, we do feel the need to make res when we have a definite destination. We mainly dry camp and not all the place we go to take res. The ones that do we take advantage of.
I do agree though that at some point it's going to get real hard to find a spot. We can still find a spot just about anywhere here in Oregon except the coast. During the week is of course a lot easier.
What I'm also noticing is on the big holiday weekends at the places that don't take res, is that they're almost filling up Thurs nigh instead of Friday afternoon.