As a rare lover of fruit cake, I can tell you it will last like a Twinkie, nuclear bomb proof, and all. Unopened fruitcakes will outlast humanity. I've never seen one refrigerated and have enjoyed them for weeks/months after they were opened. Can't imagine drying a fruitcake. I don't think any critter but a human is capable of eating such an aggregate. If in doubt, dump some rum or bourbon on it to sterilize.