I would send something out asap. I sent out my invites in June/July 2012 for my January 24, 2013 wedding. I had a rsvp date of Sept 1, 2012 and payment in full was needed by September 30, 2012. We have since changed providers and this extended the payment date, so we informally delayed our RSVP date. While a couple people jumped at the opportunity, I still have some people requesting more information, and thinking about being added to our group rate. Humming and hawing because of the money. Some people have also booked outside our group rate with a different agency, and others have booked using airmiles. Many others are waiting (stupidly in my opinion) for last minute deals to come up. So be careful if your TA is requesting deposits. We were suprised how few we actually people actually booked with our group. Good Luck