先谢谢老师的回复！
那么我再次请教老师：I-140批准 180天内或者之后更换雇主所产生的变化有哪些本质的不同呢？
-A little. If the employer withdraw the approved I-140 (within 180 days), you cannot use it to extend your H-1 beyond the 6-year limit and other benefit such as spouse cannot use it to apply for H-4 EAD. But you still can keep the priority date for your new I-140.
