I like the "go with the flow" approach as well--that way you can spend more time in an area if you like it, or go further than you expected in a day and not feel like you have to stop at the place you booked. I've only once been stuck in a town after dark with no place to stay, and I was finally able to beg a bed at the fully-booked youth hostel. But generally I've had good luck and prefer to not be too tightly tied to one itinerary.
Sarah