I booked in January 2004 for our June 2005 cruise--that was when the dates opened up. I am waiting now for June 2007 to open....so in answer to your question I would say at least 18 months...if not more in some instances.
We just booked our Dec 2006 cruise and the rates had been out for a few months prior. I actually was afraid they would have gone up before I could book!
I booked my July 2006 cruise in September 2004. It was for one of the double dip Castaway Cay cruise, which I thought would book up fast. It hasn't, but the fares have gone up quite a bit from what I am paying. The earlier, the better!
It seems like DCL opens up dates for 1 1/2 years or so at a time. We wanted to book on board for 6-06 way back in 6-04 and nothing was out yet.
Around Sept. of 2004, they opened the dates up for the rest of 2005 and 2006. Nothing beyond this.
I would imagine that with only 2 ships, they don't like to start booking too far out so that they don't underestimate the costs. Can you imagine booking really early-like 3-4 years only to have DCL send a letter to tell you the cost is now $1000 or more extra!!!! The sticker is bad enough!!!
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