For How long can I keep ganache in the refrigerator?

From my experiences, I'd say it depends partially on what you are going to do with it. Needless to say, it's best when fresh. However, I've used it for cake frosting after it's been in the fridge for a month with no deleterious effects. Be sure to keep it in a really air-tight container, no matter how long you plan to store it, so it won't pick up refrigerator odors.

In Joanne Chang's recipe (found here: https://food52.com/recipes/21949-ganache), she says you can store it in the refrigerator for up to one week.