removing a \'healthy\' breast?

I have a large invasive, lobular tumor in my left breast, stage IIb,HER2 +3, not hormonally receptive, and 6 nodes positive. I am thinking of having a bilateral mastectomy, even though they haven't seen anything in the right breast. My thinking is that I am 34 and every year increases the chance of it being there, especially being HER2, so better to do it all in one surgery now. Anyone else do something like this? I don't know if I have any genetic markers, but I have the dubious honor of being the first in my family to get BC.
Erin