I don't think there is a set schedule or timeframe. They will do the Wow Sales when they see the need for a promo to boost bookings. I'd anticipate another one in January. The best way to learn of it is to sign up for specials via e-mail at the RCI website.
Also, check the RCCL website every Tuesday. They run a happy hour special that may have some really good deals on close coming sailings. I got in on a "WOW" sail for my January cruise. I'm in a D-2 balcony cabin for under $1,200 total for my wife and I. That also includes insurance! I think Royal Caribbean gave me a Christmas present.