At least there seems to be some constitent time frame from CSC, at least as far as both our cases are concerned. My I-485 was filed more than two months before yours and I got the receipt of my second FP results at the end of July. You got your receipt early Nov., more than two months after mine.
If the trend continues, the final processing of your I-485 should happen a little more than two months after mine. As to when my application will be processed, only CSC knows, it works in very mysterious ways.