What stage you should be with your Employer and how long if GC final action dates are not current

Need your expertise,
Approved I 140 with Employer A - EB 2 priority Oct 2010
Switched jobs , currently working with Employer B - H1 B valid till 7/23
with date for filing current, Employer A agrees to file for I 485, but ask to join on GC approval.

Can you advice what stage you should be with your Employer and how long if GC final action dates are not current.

Once you get the GC, you should ideally stay with the sponsoring Employer for at least 6 months.

Thanks for your response, I appreciate your service over the blogs, they are very helpful.