There are many trade offs. The price of the cruise often goes down about 60- to 90 days before it sails, because that ios when final deposits are due and some people cancel.
However - this is not guaranteed and waiting may get you nothing. Airfare often goes up if you book it at the last minute.
The best bet is to just pull the trigger when you see a price that works for you. Either it does or it doesn't.
I am the editor, but I also speculate, ask questions and play devil's advocate. I reserve the right to change my mind.