No questions are stupid at CC! The answer is yes, no, maybe
It all depends on your recipe. If you are talking about a ganache recipe 6oz. chocolate 6oz. boiled heavy cream +about 1tbsp butter, it doesn't have to be refrigerated (btw I believe it's TWO days, not three
) But this is contingent upon your measurements being accurate. I don't know how far off they can be and still be safe. Also I have no idea if there is any alteration with regard to food safety/storage for milk chocolate ganache; I always make dark chocolate.
Of course you CAN refrigerate it, it'll last longer and then if you have leftovers you don't have to wonder if they've "expired".