I plan early so that I can lock in the rest of the trip around the cruise. Also, if you do have a specific cabin you want then earlier the better. I just like knowing that things are nailed down and I also can use our 11 month DVC window to ensure we get the resort we need for the days before/after the cruise. I also like being able to reserve the spa and Palo/Remy ahead of time and usually try to do that if we're in Nassau for a day. I have done Nassau plenty of times and now staying on the ship is just fine by me for that day.