I was wondering how long you can keep buttercream in the fridge before it goes bad.

Any help would be appreciated.

At least a couple of weeks, but it can also be frozen.

I only refrigerate mine if I'm gonna use it in a week. I usually just throw it in the freezer and that keeps for a long time and defrosts quickly because there isn't much water in buttercream.

As the other posters responded, about two weeks in the refrigerator and for me, about six months in the freezer if it is well insulated. Just remember, that once it has been brought back to room temperature you need to re-whip it to regain proper consistency.