There are ways to prevent biting when feeding live, you just have to be super vigilant.
I feed all live, but the moment they strike (if it's a poor wrap) I will hold the rat's head firmly between my thumb and index finger until it's stunned enough to stop biting. I'll also put scrap cardboard in their mouth and keep their heads angled away from the snake's body. It's a little more involved, but thawing and heating F/T is too time consuming for me.