First of all, I fully agree with jharkandi's replies to the first post, as there is no set patern or rule to when you can expect FP, or to expect approvals.
You may get FP notice within 1-3 months, but more likely it will be within 11-15 months of filing. But the main thing to note is what are the I-485 filing dates of current approval. This you can get from approval postings in this forum or from rupnet or other immigration forums. e.g. These days they seem to be adjudicating i-485 cases filed from 02/02 till 11/02. Ofcourse there are huge variations and exceptions with cases as old as 2001 and as new as 04/03 have been approved. But just to make it simpler, lets ignore these exceptions and concentrate on the majority cases.
So going by this if you filed between 02/02 and 11/02, you should expect an approval. Meanwhile, ofcourse your FP should be done and valid at the time. If not, you should expect a FP notice. Now, if your case does not fall between the range I mentiones above, you should NOT lose sleep over FP notice. So here it is not important if and when you got FP. More important is what date cases are being processed currently.
Currently the average time to process I-485 is close to 2 years. Bottomline, have patience, live your life and don't let the GC rule your life, it will happen when it has to happen. If and only if, you find many cases close to your filing dates are being approved and you still have not got any FP notice, should you worry, and not before.