I can tell you booking early saves money.
I book my trip the week after Thanksgiving every year as soon as I get home.
This year, when they extended the Free Dining up to December 17th, I contemplated cancelling my package and re-booking it with the free dining. I ran the numbers on-line and it was $5.00 more with the free dining.
I had gotten a really good room rate by booking early, so it didn't pan out.
I looked up the prices for next year, and it is the same exact price it was for this year, so I am going to go ahead and book it.
For fun, have you considered a land/sea package for your anniversery - renew your vows on the ship???? Again, booking early, you do save money.