When you warm the prey item up to room temperature bacteria starts to grow pretty rapidly. Even if you refreeze and kill the bacteria, the toxic waste products of the bacteria remain. I know reptiles in the wild often eat carrion, but to me the cost of a dead rodent isn't worth the chance of making my snakes sick.

A lot of people have a "garbage disposal" animals to take care of refused prey, such as monitors, or any other indiscriminate eater that has to be fed every day. I'm getting a tegu this summer for this very purpose.