More than likely it will expire at the end of November, 2011. I bought mine in mid-July and it expires end of August of next year. It's usually given me an extra 13th month thrown in when I've purchased it close to mid-month.
Yes, you do get more than the expected 365 days. Typically, the expiration date date is the end of the month following the one year anniversary. This goes back to when DDE was mail order only.