I am on H1B visa for 6+ years and have a approved I-140. I lost my job. And I want to take maternity break. I am planning to change status from H1B to H4 visa and get H4 EAD. After my maternity period, I am planning to find an employer who will convert back from H4 to H1B (start working on H4 EAD with this employer) and get the H1B status back. Can I change the status back to H1B even if it is 6+ years(I have a valid I-140) ?