On a trip, I will generally only book a hotel in advance for the first night and the last night. I like to hotel shop in person because you never really know what you are getting when you book online. I would hate to book a place for a week and find out the room has some flaw in terms of location, quality, noise, or some unforeseen factor. In addition, my itinerary is usually open-ended and I am not sure where I am going to be.
The risk is that upon arrival in a city or hamlet, there may be NO VACANCY. On a recent trip to Cyprus, I nearly was burned in exactly this way. Enjoy the video of Larnaca, Cyprus and hear the story of how I almost had to spend a night without any accommodation.