Spring Far Sale
Checked my e-mail archive and this year the spring fare sale went from Jan. 15 to Jan. 30 but travel had to be completed by May 8. The "summer preview sale" began Apr. 29 and ended May 8 for travel through June 25.
If next year's sales follow similar timing, you might be waiting until the end of April to book your travel for the end of May. By then, the lower fare buckets might be gone anyway. My suggestion is to go ahead and book the date and departure time you want now and when the fare sale is announced see if you can get a voucher for the difference. Make sure you are subscribed to e-mail announcements in your AS.com profile so you will be notified immediately of the sale.
Enjoy your cruise!