I called at 27 days and there were still seats available for both performances during spring break. It fills up, but not so quickly as to be hopeless if you miss the 30 days mark.
my take on this is that you are paying to rent a chair. ive been to fantasmic before, a long time ago (and totally by accident, we had no idea what it was and hadnt planned on doing disneyland at all) and it gets incredibly crowded. everyone crams into the front, i had parents telling their children to push me and get in front of me. i didnt have kids at that point, but if i did i would be very nervous about bringing them into that environment. for one thing, they wouldnt be able to see anything. for another, its crowded, and if they step away for a second they could easily get lost, or worse. so i look at it as buying the knowledge that we can sit and (hopefully) enjoy the show. im a little nervous that my kids will freak out, but i am showing them videos on you tube and talking about how to deal with the noise, so hopefully it will be money well spent for us!
Where is the seating now? Now that they don't do the buffet on the balcony, did they increase the "on the grounds" seating? Is it still possible to get a good seat on the ground for free in front of the River of the Americas?