No Title
I got my I-485 Approval a few weeks ago. I asked the same question from my lawyer. She said that I should not leave my employer for 6 months after I-485 approval (It doesn\'t matter when your passport got stamped, the 6 month starts with I-485 approval).
I asked what if the employer lays me off or fires me? She said that\'s OK. You did not leave the job, they laid you off and you could not do anything about it. In that case, after you get laid off, you can do anything you want and get any job you want. You can go to Burger King and flip burgers if you want.
I would recommend staying with your employer for another 6 months just to be safe. Unless you have a really really good job waiting for you; in which case you can try to get yourself fired :-(not recommended).
Hope this answers your question.
--Username