@Fernweh
The decision for a preventative mastectomy is intensely personal, so what others have done doesn’t necessarily give you a solution. I had a single mastectomy. I had the surgery three days after confirmation of my biopsy, my surgeon never mentioned bilateral surgery and I had no family history of cancer at all. I was too busy about having one breast removed to think about the other! After surgery, quite a long time after, I discussed the possibility (for interest rather than commitment) with my oncologist. His view was that I had as strong a chance of a new cancer in another part of my body as I had in my right breast. More than nine years on, and so far NED. The major issue is, I think, that I could live and function with the possibility of cancer again. I can’t remove all the parts of me that might get it. But if I had felt terribly anxious about my breast, removal may have helped me to live with all the other uncertainties that cancer is so good at reminding you about! You’ll find your right answer. Best wishes.