thanks for the quick response and the info, poon_hill. i have a follow-up question - do you know anything about extension (H1B) beyond 6 years? I'm sure extension after hitting the 3 yrs mark isn't a problem. But what if, for some reason, someone fails to complete their PhD within 6 years? Is it possible to extend further, or can one apply for a F-1?

kiddo, i don't think they teach H1B to PhD students 
elaborate? i'm having hard time understanding what you're trying to say, bro.