H1B after L1

[BMR]

Hi,

I've two queries -

1. I was in USA on L1 visa for 5 years. Then I came back to India. In the same year my company filed for my H1B. Got H1B approval from Oct-1, 2012 till June 30 - 2013. Am in India since may-1st 2012. So my question is when should I go back to USA to get maximum period there in USA.

2. Do I need to go to USA at least in March 2013 so can file an extension as the I-797 end date is June 30th 2013

please let me know if need more details.

Thanks for your help !!