Store cinnamon butter at room temperature for 1-3 days. If you haven't devoured it by then, you can keep it in the fridge for up to 1 month.  Freeze for up to 6 months.  Whether it has been chilling in the fridge or kept in the freezer, but sure to allow it enough time to soften before serving. Reheating in the microwave is unreliable and you can end up with butter soup so don't do it.