In the past I have always froze my cakes after filling them and crumb coating with with swiss butter cream. I would then cover them with fondant and stack them (if they were multi-layered and put them in the fridge). Depending on the fridge temperature, this usually caused a lot of sweating. I want to leave the cakes out after they are covered but I'm afraid the soft butter cream underneath will not withstand on its own, and once softened will look bumpy? Is this true? Does anyone else leave there fondant cakes unrefrigerated even if they are filled with butter cream? Any tips or suggestions? 

Thank you

I use meringue bc's exclusively and always refrigerate. No, they don't lose their shape or get bumpy. I time my deliveries so that the cake will be as close to serving temp as possible. So they are sitting in their little place coming to temperature.

I refrigerate fondant cakes all the time. As long as you don't touch them while they're warming up to room temp it doesn't matter if they're covered with condensation or not. It will dry out eventually.

Ditto, refrigerate Satin Ice and SMBC cakes all the time with no issues (in Alaska and it's dry though).  It will definitely not get lumpy at room temp.