Hello again, Danielle! Free upgrades are actually not that common. The one you are speaking about happened last week where select guests who were staying at a value (I'm not sure if it also included moderates), received an email offering a free upgrade to either Saratoga Springs or Old Key West. When these types of offers come out, there are usually only a few rooms available for any given night (so if you ever seen one, you'll want to act on it right away).
Another type of upgrade happens within your resort where you may be upgraded to a different room within the resort. For example, at All Stars, if you booked a standard room, an upgrade would be a preferred room.
I personally have never asked for an upgrade. However, I've been lucky enough to receive room upgrades on a few occasions. I just let the magic happen...and if it doesn't, I know I'll still have a good time with the room I booked.
I'm going to send you lots of pixie dust your way for a potential upgrade. Good luck! Diane :)