Since ganache is made with cream, does it need to be refrigerated after getting the cake decorated?

My understanding is that because the cream is brought to boiling or near boiling point when making the ganache it changes the structure of the cream and so it no longer needs to be treated like a dairy product. So no, I don't think you do have to refrigerate after decorating. Refrigerating will give you a nice hard surface to cover with fondant though.

No Ganache is good at room temp for a couple of weeks .

No need to refrigerate. I would only leave it out for a few days. It's cold right now so maybe a little longer.

Thanks guys