H1-B Extension and Visa stamping

[immi-help-needed]

My 6-year H1-B will expire on 09/30/2012 and I will apply for the 3-year extension soon based on my pending AOS application. Once I get my H1-B extension approved, I plan to get my new H1-B visa stamped at a US Consulate in Canada. My question is how early I can get this new H1-B visa stamped before my current H1-B visa expires? (I read that one can go as early as 90 days for their first H1-B stamping before the validity start date. Is it true for the H1-B extension as well?) Can I go to the US Consulate in Canada in 07/2012 to get my new H1-B visa stamped, even though my current visa does not expire until 09/30/2012?

Thank you for your time and help.

[Attorney_10]

Generally, it is possible to apply for a visa extension prior to the expiration of one's current visa in his/her passport. The U.S. consualte may issue a new visa valid for a longer validity period (i.e. from present to the expiration of the latest approved H1B petition). Please contact the specific consulate webpage for more details.