Once a week, as Brassard recommended to both of us. It did, however, take me close to the two-year mark to get to that point; before that I spent at least six months at twice a week. I honestly think when he says "taper down," he basically means most women will get there eventually, but we'll have to listen to our own bodies to see when it's possible.
To be perfectly honest, the main reason I got down to this was that I went on a business trip for a week and figured that even though I was still a little scared to try, I'd wait the whole week and dilate when I got home. 🙂 It worked out fine, and then I stuck with once a week thereafter.