I have a hard time when you try to tell people that they should book a cruise early and they don't listen. I have found that at least with Carnival Cruise Lines I can book early, if the price they are posting is one I am willing to pay, and that if the price goes down I can get my price reduced. I have people that always think that if they wait the price will get lower and they will get a better deal. Well I can still get the deal they get if it goes down but more often than not I will end up with the lower price and the better deal, ie. on board credit, cabin upgrades etc. I am not saying that price doesn't ever go down but during the holiday sailings they tend to go up in price. So why take the chance if it is a vacation you know you want to do. Book early and just keep an eye on the prices. If you see the price go down contact your travel agent or if you are like me you just submit the form online to get the price adjustment. We just took advantage of the National Cruise Month sale on Carnivals website and got the upgrade, onboard credit and 1/2 price refundable deposit.
I also always check airline prices when they first come open and keep checking to see when I think the price is the best deal I can get. Unfortunately we travel at the most expensive times of the year Christmas and summer. So I know that more often than not airfare is the cheapest on Christmas Eve or Christmas Day. This next year we will not be so fortunate to be able to fly out on those dates since our cruise will be leaving port before then. We also do not have a big window of time that we can fly out so I am totally at the airlines mercy. I wish Southwest flew out of our airport just for the savings of checked bags.