I was just wondering if anyone has ever frozen a fondant covered cake and then used it 2-3 months later with success.

I did it once. The first cake that I ever covered in fondant was just for practice anyway, and I knew that we wouldn't be able to eat right away (we were going out of town or something), so I froze it for later. I wrapped it in layers of plastic wrap and aluminum foil, and when I took it out (I can't remember how long it was, maybe a month later?) I let it thaw with the wrappings on to reduce the amount of condensation forming directly on the cake. It was okay I guess. Being my first fondant cake, it wasn't that pretty to begin with, and the fondant did end up kind of shiny. I wouldn't have served it for a party or anything, but it was okay for us to eat at home. I don't think I would try this for any sort of cake I was doing for someone else. I have read in a couple of places that you can do it, but I think if you don't have to it would be best to avoid it.

Oh yeah, another thought, if you do have to freeze (or refrigerate) it, I would not do it with any sort of icing decorations or painting or anything like that on it, especially if they are very bold colors, because as it warms up and condensation forms the colors will bleed and you will end up with a mess. HTH!