If you find yourself on a cruise and really enjoying the experience, then you might want to consider going ahead and booking your next vacation. You can book your next cruise while you're still on your current cruise to take advantage of discounts. The best part about this hack might be that you don't even need to book a specific cruise or destination. All you usually need to do is put down a small deposit.
You can decide exactly where you want to go later. That cruise line is just trying to lock you in for another cruise, and they'll offer some pretty sweet deals and discounts to do so.