The bummer part about taking classes is you have to make your flight and hotel arrangements way ahead of when they actually release the list of classes and teachers. They currently have a list of the teachers who will be teaching this October, but they don't have a list of the actual classes.
If you decide not to take any classes, then just purchase your tickets, and yes I recommend not purchasing at the door.
The first couple of years we went, we would spend a couple hours at the show, then we'd walk over to the vendors and spend a couple hours there. Your brain just goes on overload if you look at the quilts all day long. If you see something you like in the vendor area, but aren't quite sure you're willing to buy, write down the booth number and the item, so you could return later to purchase it. I did this one year when my fun money budget was very tight and I needed to think about whether I really wanted a particular item.
Make sure to build in break times, so you can sit down and relax. You'll last a lot longer. I used to bring my Kindle and read for about half an hour, then go back to the show.