The problem with trying to book ahead is you cant always be sure you will be where you think you will be. We did 10000 miles last winter, and are doing the same this year. We are from Ontario, and are currently in Needles California. We never make reservations. We took a week to get to Flagstaff from Ontario. This was putting a few 8 hours days driving at first, then doing four to six hour days after that. We wanted to see some stuff along the way, and driving 8 or 10 hours a day, you bypass lots of interesting things. We have 8 weeks in total. Dont kill yourself getting there, or you will be tired for a few days. You might as well take a few extra days to get there and be fresh. Back to the reservation aspect. Last year we hit a chunk of metal on the road and blew a front tire. This set us back a day. We had a problem at one campground. The disconnect relay went and we couldnt retract the slides. This set us back a day and a bit. In New Brunswick years ago, we blew a transmition. This is the problem with reservations. If we had reservations, we would have had cancellation fees due to not being there on the date reserved. If the whole trip was reserved, you would have to skip something to get back on track. We have travelled probably close to 45000 miles in the last six years, and have never made a reservation, except calling ahead either the same day, or maybe the day before if you are sure you are going to get there. The only time we have had to stay at a rest area or Walmart, is if we wanted to. Buy a National park pass, it is worth the cost if you want to see the parks. It doesnt cover camping, but gets you into many great things.