The date only matters because Disney needs to be able to see the ticket in their system. When I went in March our Cheaptickets (same company as Orbitz from what I understand) voucher had not yet shown up in Disney's system so it took 3 CMs and 45 minutes for them to contact Cheaptickets to confirm our tickets. We bought the tickets about 2 weeks in advance of the trip. I also tried to pick up my son's ticket that day for our June trip, but they wouldn't let me. Since that didn't work, I was going to try to pick it up when I was there in May (which would have been 3 weeks before our June trip), but it was the 24hour celebration and I was completely focused on that and forgot to do it. We had absolutely no problems when we finally did exchange the voucher during our June trip. The CM totally knew what he was doing and was very efficient. We were there on the dates that were on the voucher though. To be honest, I think it may just depend on who you get at the ticket window. I think enough time has also passed that your tickets will be in their system so I can't see why it would be a problem. Good luck and hope you all have a wonderful time!
Also, in case this comes up...we bought our son's ticket before the price increase. When we added a day to the ticket, we lost the discount. They only gave us credit for what we paid for the ticket pre-increase, so I ended up paying the full price anyway! (I did keep my Ebates credit though...I don't think Disney has any way of tracking that).