How long does frankenboob last?

At 8 days you are about 5 percent settled, shaped softened, dropped and fluffed. "Drop and fluff" refers to the fact that as the skin stretches and the muscles relax, the implants move down and out slowly – about 1 percent a day. It’ll be about six weeks before they even begin to settle down, but they’ll be close to 80 percent settled at three months. Watching their progress is like watching your hair grow. You don’t see a difference in your hair growth daily, but all of a sudden you need a haircut. 
Be patient after surgery. Give yourself a few months before making a judgment about your surgical results. You won't know the outcome until then.
Dr. Ted Eisenberg, Board Certified Plastic Surgeon and Author
Phila., Pa.

It can take several months for the two breasts to settle. If conncerned,then you are best seen by your surgeon in person.