I was told once you can be upgraded if you have traveled with the same cruise line. How does this work? Smile
The only upgrades (up-decks) based on being a past guest I've received from Carnival have been when the price I paid went down. Now those were based on the Past Guest rates and they added the up-decks to the Category I had booked.
Now they do give a little priority for those on the secret list for being past cruisers. Well it actually isn't that big of a secret. If they have no-shows for the cruise after the first port call they will give them to people on the list that have asked.
Once you've cruised on Carnival you will be eligible for the Past Guest Rates that often include up-decks.