That is supposed to be what happens. The AP voucher only becomes active once you go through the turnstile with it or take it to the ticket booth. It should then be good for one year from that date of first entry. We had some problems with this though when we redeemed our vouchers on August 10. You might want to look at the first half of my first post on this thread:
http://www.disboards.com/showthread.php?t=2781142
I guess the lesson is to read everything carefully and make sure you get what you paid for before you leave the ticket window with your new pass. Honestly, since you have to go to the ticket booth that day anyway to get your actual pass, there isn't any advantage to buying online EXCEPT to be able to enter the park and do some stuff first before having to deal with the administrative stuff. If you're going for rope drop, then pre-purchasing will help you get into the park quicker, but if you're not as worried about your place in line at the turnstiles and/or plan to be in the esplanade at least a half hour before DL opens, then you might just want to wait and buy at the ticket booth. There is no price difference on APs for pre-purchase. The only reason we did it was to beat the June price increase.