Great job on lowering your loan rate!
Instead of choosing a Celebrity cruise, consider looking into Princess and Royal Caribbean as they offer great value for the price, especially the beautiful Ovation of the Seas.
For us, a balcony cabin is sufficient since we spend most of our time out and about. By saving money on the cabin, we can afford to extend our cruise duration.
We typically reserve our preferred cabin a couple of years in advance when the cruise comes on the market. During the two years leading up to our cruise, our travel agent and I keep an eye out for sales. If we find a genuine sale, we can apply the new fare to our booking as many times as we want. However, be cautious of tricks where cruise prices increase when extras or on-board credit are thrown in.