Min. time that should be left on H1B WP Ext before I can go for Stamping?

My H1B WP extension is expiring on 1st Nov 2012 and not yet stampped. What is the minimun time that should be left on H1B WP before I can go for stamping. As only 4 months are left on my current H1B work permit, is it advisible to go to India and go for stamping in Aug 2012?

If I am granted a visa then can I face any issues while returning back to US in Aug/Sep 2012?

Or Is it advisible to apply for H1B extension before I travel to India?

Thanks,

Ankit

Its better to have your H1B extension filed before you travel to India.