Can peanut butter icing be stored at room temperature or should it be kept in the fridge?

As long as you are using this icing on something that is ok being left out at room temperature, this icing will do just fine left out. It should remain fresh for up to a week, at least. Just be sure to cover the item well - in an airtight container is ideal. Wrapped will with plastic wrap is a good option, too.

Any unused icing can be stored in the fridge for a week or two before using. Just be sure to store it in an airtight container to keep it from getting dried out.

Can I freeze peanut butter icing?

Yes! Whether you have iced something or just want to make this ahead of time and pull out when needed, this peanut butter icing freezes nicely. Make sure to freeze it in an airtight container.

If you are freezing it to use for later: Remove the icing from the freezer and allow it to thaw completely before use. I'd recommend throwing it in the mixer to stir it up again or by hand with a whisk or spatula before using it like normal in a recipe.

Can I substitute sugar with another sweetener in this peanut butter icing?

Yes! I recommend using a powdered sweetener, such as Swerve, as it measures cup for cup in the place of powdered sugar, I believe. Just follow the instructions on the package for exact conversion ratio.