I looked into it for our stay in September and was able to book a date but decided against it as we have done it before.
Two years ago when we went, like PP, we would call and be told they were sold out, then unavailable, then the dates hadn't been released. Then one CM was very abrupt and said it was 60 days NO QUESTION. So we wait until 60 days, (lesson learned) and found out the dates had been released around 90 days.
We DID end up getting a spot for that trip so it worked out, point is, unfortunately, it is a scramble with no apparent rhyme or reason!