Like Dave said, they have the doors closed for access to most cabins. We are Platinum and we have had mixed results. Once they let us go to our cabin a little early (like 1PM) But other times we waited until 2PM. It may totally depend on where your cabin is and if you can get to it. I have been told they do try to have the Platinum guest cabins available early.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013