Just to clarify, the freezer you are referring to is called a "Chest Freezer". It is a name that comes from the original freezers that were the shape of a chest as most still are today. (and no, I am not going to look up a date)
Deep freeze is a term given to (as mentioned before) a much lower (deeper) temperature then a domestic refrigerator.
Now, to answer the question, mice can safely be kept in a chest freezer for 6 months (assuming normal operation of the freezer). Some people will argue this info and have/will keep mice longer in a freezer, they will start to deteriorate to some degree. Any feeders can have a prolonged "freeze life" if they are vacuum sealed. To avoid any misconceptions, vacuum seal means removal of all air, thus removing all oxygen that will sustain bacterial growth.