Hi Melissa,
I am in a similar spot as you. After a year, I am still having bad headaches. The doctors think that the bone piece that they returned to my head at the time of surgery failed to get a blood supply and has dissolved. (at Mayo they replace the bone rather than use fat) That has caused continuing irritation/damage to the dura (lining around brain, inside skull). We did discuss that I may need a cranioplasty to help with my headaches. However, I was in no hurry to have anyone reopen my head for a "possible" cure, so we agreed to give it time to heal. By cranioplasty, I mean that they open things up, scrape scar tissue away, insert acrylic material between the dura and the mesh, and then close you back up.
The theory, from what I can understand, is that the bone (or in your case, fat), fails to become integrated into your body and dissolves. The titanium mesh or scar tissue, without a buffer (ie skull), is then directly touching the dura and causing pain. However, the pain could also be caused by the nerves being cut and damaged at the site of the surgery. So, I don't believe it is proven, but one of the current attempts at trying to figure out why some of us have such bad headaches long term. From what I can tell, it helps some people and not others.
So, I can't tell you about the effectiveness of the surgery, but I am familiar with what you are talking about. I look forward to hearing about anything you find out as you continue forward.
I'm still grappling with this issue myself, so I stand corrected if anyone has more definitive information!!
Samantha