Guarantees - are not really upgrades.
On a guarantee they just assign a cabin in the category you purchased or better. I have had cases where I dont even know the cabin when the people board the plane. It is assigned at the dock. Most of the time it is assigned somewhere between 6 - 2 weeks before departure. There is really no pattern it can happen at anytime.
An upgrade from a confirmed cabin number
On a complimentary upgrade from an actual cabin number normally they will call the TA and confirm that the client wants to accept the new cabin. This is true even if it is an obvious YES. A change for instance from an H cabin Voyager to a midship F cabin. They still call. People have attachments or reasons to be in certain cabins and dont want to move no matter what so a call should be always be done. This is normally only done when THEY NEED your cabin for a reason. For instance someone doing four back to backs and wants cabin 601. The only segment 601 is not available is the cruise you are on in and you are in 601.They need you to move out of 601 to accommodate the passenger taking a longer cruise so they offer you an upgrade. Or a family of five cabins and they want to be together and your cabin is in the middle of their cabins. Things of that nature.
A paid upgrade for less prior to boarding
For a little while they were calling and offering upgraded cabins for a fee. Particularly suites. A lot less than the normal charge. It happened for a couple of months and then stopped. Whether it was an experiment to see how many would pay just a little extra for a better cabin or whether the ships are so full now they dont have the space I really dont know. Not had a call like that for a long time. (This is what Joanna was talking about in her post above) You cannot request this it was just an action they decided to take.
Then there are things like Betty's. She was upgraded we were obviously not informed or we would have called her and let her know. Why we were not called who knows, just slipped through the cracks I guess.
