Hi Guys,
It really depends upon which center you applied and which regional office you went to get your passport stamped. I read in this forum that some of the guys from Vermont service center got GC plastic cards with in 2 months from their stamping date. However, I have been told that average time for Nebraska guys is about 6 months. My friend who applied in Texas center, but got his passport stamped here in Denver office received his card with in a month. However, I got my card four and half months after I got my passport stamped at the Denver office ( I applied in Nebraska center though).
So, it really depnds upon service center, regional office and most importantly, our luck too, by that I meant the officer who took up your case.
Regards and best of luck.