Not really, not if you're making the kind that has 2 parts chocolate to 1 part cream by weight. I make this stuff all the time and have no problem with it. Left out of the fridge (which is what you have to do or it will get as hard as a rock), it takes on the consistency of peanut butter from one day to the next (or even in a few hours). I work in an un-airconditioned kitchen in Cancún and often take my cakes to outdoor parties (with shade, not direct sunlight) and I always use ganache under my fondant. It softens a little bit, but not like buttercream would.