What is the best way to store a cake with ganache? I am making one today/tomorrow my dh wants ganache and chocolate details.

refridge is always best with ganache just make sure to keep it covered like a box otherwise it could pick up flavors or smells from your fridge

I have heard that they did not need to be put in the fridge.

I prefer to put them in the fridge.

There are not many circumstances where I don't store in fridge at some point. It's all about removing them from the fridge at the proper time to let things come back to a proper serving temp and consistency.