自己搜了一下，貌似有个网站是这么说的。。。
I-140 revocation
Approved I-140 petitions are no longer automatically revoked when an
employer withdraws the petition or the business terminates… But only if the
withdrawal or termination occurs 180 days or more after the petition was
approved, or after an I-485 adjustment of status application has been
pending for 180 days or more
There is a difference between retaining a priority date and retaining the
validity of an I-140 petition approval. The rule clarifies how a priority
date is retained and how this differs from the provision that addresses what
constitutes I-140 revocation for purposes of I-140 portability cases.
