I'm with Nazpaz...I enjoy the planning and find it enhances the relaxation to know everything is taken care of, no hassles searching for a decent site. I'm good at estimating how long we may want to spend and I build in some days to relax, do laundry, watch football, clean the RV. It works out fine.
We book everything ahead and get to stay in wonderful places that way...oceanfront state parks, for example. Only once have we eaten a pre-paid campsite and lost $20 or so, because we decided to head on home a little sooner than planned at the end of a two-month trip.
That said, after three years of structured, wonderful trips, I'm thinking about winging it next summer/fall to the Gaspe Peninsula. But I'll have a plan outlined even if I don't book ahead long in advance.