As I was moving to the next page of posts and checking my reservation in another window, I was thinking "I should just post and ask how far in advance it might change from a GTY". Lo and behold this thread was at the top of the next page!
Thanks to everyone for the answers. I'm still months away and now that my full payment has been applied, I could probably stop checking every day! It's a habit now, though, so unless they notice at work and tell me to stop, I'll probably keep checking!