It really depends on the snake. I personally don't see any harm in trying to feed them. Some will take it some won't. My rescue hadn't eaten in 2 weeks so I tried to feed her and she ate. I've had some snakes come from breeders that eat even after being shipped and others that make me try several tricks before they will take food. So as I said, it really depends on the snake.
I don't refreeze anything. If they don't eat it I will toss it or offer it to someone else (I don't offer refused quarantine food to my collection or the other way around).