I believe its 60 days for Dining and 30 days for Fantasmic and most tours. I could be wrong but thats what I was told when I was planning our upcoming trip.
Since you are staying at PP you can call Vacation Planning and let them know what you are interested in and when you would like to do it and they will book it for you as soon as it opens up. I did that for this trip and it worked out great, I had them call or email me to confirm the seating and if they didn't I would have called them just to make sure they did it but there were no problems and I got all of my resies that I wanted.
Good luck, sorry I don't have Vacation Planning's # with me right now but I am sure someone out there has it or I know it was mentioned on one of the other threads.
Aloha Zena