I think it depends on where you are booking, and how close to the holidays you are going to be. I know in Negril, everything is fairly easy to book close in time, EXCEPT the photographer... they book up quickly. And I know a lot of resorts that handle weddings on a regular basis have a lot of vendors on site/regularly work with, so I guess as long as you pick out a date that the resort has available, you will be fine...... But the issue with a December wedding and booking late, in my opinion, is how it affects your guests. They need time to ask off work, make travel arrangements, etc., which is further complicated in December because of the holidays. So long as you don't mind that some people may not be able to make a wedding with little notice, I think you can book as late as you can find resorts with openings. Good luck!