This homemade hot fudge will keep for a month in the fridge unless you eat it all in the first two days, which is a very real possibility. I have been storing mine on the counter at room temperature for two weeks and it's fine. I'm sure someone will ask me about refrigeration for gift-giving. I don't know, so do what feels right to you. To me, the extensive boiling process renders this okay to store at room temp, but store it how you're comfortable!  If you do store it in the refrigerator, it'll firm up and can be reheated before serving. I recommend scooping some into a small cup and nuking that portion for 15 seconds rather than reheating the whole jar over and over. This will keep the rest of the hot fudge sauce fresh and will prevent it from clumping up from being reheated time and again.