Is it mandatory to travel US 6 months before H1 visa expiry?

Hi, i got my H1 approved in Oct 2012, however the status in USCIS online did not get reflected til Apr 2013. I got it approved now but my H1 expires by Dec 2013. Is it mandatory to travel to US 6 months before H1 visa expiry? Wont they grant me entry to US by Sep 2013 and then can i apply for an H1 extension immediately? Please provide me the norms as im afraid if my visa will be wasted??

There is no 6 month duration. You can enter US as long as the petition and visa stamp is valid and your employer can then timely file for H-1 extension. Discuss w/ employer when they want you to start in US.