If spoilage is a huge concern, get your rats here:
http://www.themousefactory.com/
They vacuum pack them, and I've never seen such gorgeous mice and rats--they look like they went to a beautician before they were frozen, lol.
They're only a bit more expensive than RodentPro, and EVEN WITH shipping costs, they STILL cost less than what you paid for yours.
Buy 6 months worth--they'll keep perfectly, and you won't have to worry about it.
I use RodentPro, but I have 41 snakes. If I only had a few, I would use Mouse Factory, because the quality is higher and they keep longer.