Can I get an existing stamped visa stamped again for extended period under new employer

USA H1B Visa
1

Hi,

I got my H1B sponsored by compnay A in 2013 Oct for a period of 1.5 years. I went and got my visa stamped in November 2013. In April 2014 I got my H1B transferred to Employer B. This time I got an I797 for 3 years.

  1. I am going to India in November 2014. Do I need to get my Visa stamped again given that the original stamping for 1.5 years is till valid till March 2015.

  2. I need to go to India again in April 2015 when the existing stamping period will be over. So I wanted to get my stamping done while I am in India in Novembver 2014. My question here is- can I get my visa stamped for the new 3 year period under my new employer while my existing stamped visa is still valid.

Thanks a lot in advance!