I rode pretty long days, but there are so many points of interest and places to stay that one can go at pretty much any pace. Hotels can fill up in July, so you might want to book ahead. Lonely Planet usually has some good tips for bike touring, though I'm sure there are all kinds of bike-specific guides to the Loire as well. I took a bike (this was back when People's Express was like $99 from Newark to London Gatwick), but there are probably all kinds of rental options there. That part of France is perfect for bikes.