While I subscribe to early booking being most advantageous form pricing and the ability to take advantage of (increasingly unusual) price drops before final payment, I will agree that booking last minute / post final payment date can offer deals. However, I would argue that the savings come with other costs.
First, the cruise you want may sell out - and this happens a lot.
Second, if cabin location / choice matters to you this is unlikely to give you the vacation you desire. Think about it. What cabins are likely to remain unsold? The ones everyone else doesn’t want. Cabin location matters a lot to me, and I’d never book a GTY because of that, and playing kamikazi with last minute cabin availability isn’t for everybody. True, a great cabin might show up via a last minute cancellation. But if I want to gamble, I’d rather do it in the casino than my cabin.
Third, airfare. Last minute airfare tends to be higher than further out. If you have to fly to your cruise, the savings on a last minute cabin fare could be more than eclipsed by the cost of the flight.
Fourth, everything I just wrote goes out the window if you live in Florida. If you can drive to multiple major cruise ports, have an openness to destinations, and don’t have a preference in regards to cabin, you can game the system. As far as I see, cheap last minute cruise opportunities would rank as the number one reason to move to Florida. I have to believe that I the few days before the cruise, aside from the requirements to have a set passenger list 48 (?) hours before sailing, there’s got to be a last minute spot to be had at big savings.