Does anyone have access to reliable research about the anti-bacterial defences in a snake's digestive system? I would expect that putrefying bacteria would be unlikely to thrive in the digestive juices found in a snake's stomach. Even snake saliva may have anti-bacterial properties - mammal saliva does, I believe. Also, I have heard that monitors can safely eat dead animals in advanced states of decay.
My guess is that toxins already produced by the bacteria before the food is eaten are more of a danger than any living bacteria, but I don't know what natural defences snakes may have against them, either.
I have never needed to feed thawed food more than 13 hours after initial thawing and, if the situation arises where my snake refuses a night feed and refuses again next morning, I will throw the food item out.