If it did anything I would expect it would just extend the amount of time by 48 hours. If it doubled the damage everybody would be plowing all kinds of pet food into it. I suspect if you tried, and it couldn't use the second, it wouldn't take the second as the "slot" (for lack of a better word) for the pet food would be filled. Not that I've tried so it's just my sense of the matter here.
AJ