I pulled this off of Rodentpros website. Depending on how they are stored, most frozen feeder animals can last up to a year. It is a good idea to minimize any exposure to air by ensuring they are in air tight freezer bags. While we recommend not storing feeder animals without fur for more than 4 or 6 months and feeder animals with fur for 9 to 12 months, if properly sealed containers are used and air exposure is kept to a minimum, they can be kept for much longer.
I just order 3-4 months worth and have no issues. Hope this helped.

Matt