I was at CCRM and I tapered starting at 8 weeks before finally going off of it at 10 weeks.
From what I recall, 8 weeks is when the placenta has most definitely taken over the necessary hormone production, although they think it may actually happen a bit before that. No one really knows.
I had some spotting as I started to taper and was worried it was related, but RE said at 8 weeks, my body was definitely doing this on my own.
Not sure how I'd feel about tapering after 2nd beta...