ar888 said:I never wanted to get in to this job change discussion, but..
The intention of AC-21 is to avoid the inconvenience/suffering to the applicant (in changing 'intent'/jobs) due to the extraordinary delay in GC adjudication. This is the reason, they said, I-140 should be approved and I-485 should be pending for 180 days or more to change the jobs, as long as the job falls under 'same or similar' category. Here the 'Same or similar' concept defines that the new company is your sponsor going forward. And once approved, you should have 'intent' to continue your employment with the company.
But one the GC is approved, the scenario is different, there is no concept of AC-21 here, as there is no inconvenience to the applicant (as he is already an employment basedGC holder). And again the applicant should have 'intent' to stick with your sponsoring employer, as the GC based on your employment (similar to Family GC is based on your Marriage).
And again, there is no 'rule' that how long you should stay with your employer. Individual circumstances may vary, that is the reason, 'rule of thumb' comes in to picture.
Since already it took more then six months, inconvenience is already caused which is irrecoverable even after the approval.
We are missing an important Intent of AC-21 which was to clear this hurdle for going into the better opportunities. This was not just prior to the approval but continuously.