How long can they stay in the freezer for until they begin losing their nutrition? I only have a single BP that is eating large mice right now, f/t. The problem is a pack of 4 of them is costing me $11, and after looking at some prices online I was thinking about buying larger and more cost effective. My concern is them going bad or losing their ability to satisfy his requirements after a certain amount of weeks. He eats 1 every 5 days right now.