PERM in process..When to switch employers?

[sid1980]

I am in the 6th year of H1-b (expiring on 15 May 2013) and my PERM application was filed on 7th Mar 2012. If the PERM and I-140 both get approved prior to the H1-b expiration date then will I be able to switch employers. If a new employer applies for a H1 transfer then will I get an extension only till 15 May 2013 or will be I eligible for more getting a 3 year extension based on I-140 approval?

[Shruti1983]

To get extension via company A you need to have an approved I-140 from company A.