I appreciate comments from Jaxen and found something supplemental. While reviewing faq on this website I came across with a question which I am posting below that sounds like giving benefit of doubt / confusion to employee. Hope this will let visitor of this site to have more info and also I am expecting someone to share their knowledge and experience further on the implications of having gap between first and second EAD's.
Thanks in Advance, ................
Q: Do I have to get an EAD if I file for adjustment of status?
A: No. Once you have filed for adjustment of status, there are no additional penalties that attach if you fail to maintain lawful status by letting your nonimmigrant status expire, or accepting unauthorized employment. Your employer, however, can be penalized for employing you without permission.