With proper storage, most cookies can be kept in the freezer for up to three months. The best way to store cookies depends on the type of cookie you're baking. For example, chewy bars should be stored in a single layer in a covered airtight container. Most cookies, however, can be stored by stacking them in layers separated by wax paper and sealing them in a covered airtight container.
Also check out how to freeze cookie dough.