Let me add here...
With AC21, you can leave company anytime after 180 days of filing 485 as long as you take "similiar job" with another company. "Similiar job" can be demonstarted to INS with help of showing new job matches with that of old job\'s ETA-750A. But if you dont intened to stay in same filed then most lawyers recommend at least sticking with company for another 6 months once you receive stamp in passport. The INS ruling of staying with same company for 2 years after you receive your GC is outdated now. If you intend to leave job right away after you get GC, INS considers this as fraud (Your GC might not have approved at first if INS had known this!). But if you stay 6 months, then onus is on your Employer or INS to prove.