The main advantage to sleeping at a control is certainty. You can get your card stamped and go to sleep and not have to worry about being late to a control. I think only Loudeac on the first day has a problem with availability, because it's the natural sleep spot for most people. They don't disqualify you for being late to a control on the road any more, and I think all you have to do is finish in time. But they don't tell you that.
I wanted to sleep at Tintineac on the way back, but there was no way I was going to make it. I was just too tired. I have no trouble going to sleep right away even in a big room full of randonneurs that snore. It's the best thing that I have learned from randonneuring.
TIL my name is "cave" in French. I'm not sure how to use this newfound knowledge.