I live in tropical north queensland where it humid nearly all year round. I never put my completed work in the fridge due to the condensation. I have a very sturdy butter cream recipe that calls for copha and royal icing powder to stiffen it. Or i use a ganache. I work and store my cakes and cupcakes in an airconditioned room:)
Karina, Australia, Just Peachy Cupcakes, http://www.facebook.com/pages/Just-Peachy-Cupcakes/137948552921588