Many times I've seen amazing deals on cruises. Usually the cruise is perhaps a month out or even a week away. Do you have the kind of lifestyle that allows you to cruise at a moments/weeks/month notice?
There is an online travel sight that has a 90 day ticker. I sometimes go there and dream about where I can cruise in a week or a month. I have the mindset that can pack and go in two seconds flat. However, my work, my family may not second my idea.
However, if you live in a home port area, (Florida, Baltimore, New Orleans, Houston, London, etc.) you should consider this as a way to save on your next cruise. Airfare significantly increases your vacation budget (I know, I live in northern Michigan where the closest major airport is a 5 hour drive...sigh.) so if you can do without that component, you're already ahead of the game.
Check your favorite cruise line and do a dummy booking to see if you'll save on a cruise that is within two months. I retire in 4 years with plenty of good years ahead of me, God willing, and I plan to move to Florida as soon as I can.