Variety is a good thing. Especially if they decide they won't eat something for a little while you always have a back up. Mice is our snakes staple food, but they also get fish from the safe list, and night crawlers. They offer different nutritional values. While mice are the most complete nutritionally, they get good stuff from the other options as well. Variety is a good thing.

Night crawlers will keep for a long time in your fridge. I don't feed exclusively worms in one feeding, so others may be able to help you with the quantity to feed.