I was wondering if it is possible to freeze a cake once you have iced it or put fondant on. I'm trying to work out how to make 150 mini cake and a big cake for a wedding.

If it is possible how long will it keep in the freezer?

Thank you for taking the time to answer me.

The grocery store and Wal-Mart bakeries freeze decorated cakes all of the time. I'm not sure about fondant but I've read here in the forums that if the fondant is Satin Ice you can freeze it. I think it was Leah_S that said that. You may can freeze other fondants as well, but I'm no expert in that area.

I have frozen cupcakes with buttercream or IMBC and they are fine. Sometimes however I have encounted some condensation on icing once defrosted, was quite humid here though, maybe I should've placed in fridge for a while before bringing them to room temp?
I wouldn't freeze cake with fondant. At least with the brand of fondant I use. I don't even place fondant covered cupakes in the fridge. They tend to sweet and decorations seem to go soft.

If your sugarpaste contains glycerin, than you can not put your cake in a fridge.

if your cake is covered 100% in fondant I would not recommend it. If you have only fondant decorations then add them after you take it out. They will last forever dried.
If it is buttercream then yes, you can.
Just make sure you thaw it in your fridge and that will help avoid condensation.