Dear Home Ec 101:
How long will butter last in the freezer?
~Freezing my Assets
It depends, at 0°F butter will last 6 – 9 months and still retain its quality. I have frozen it for much longer with no noticeable change, but our deep freeze is only used for long term storage. If a freezer is frequently opened, food may lose quality due to exposure to moisture or fluctuating temperatures.