Personally when I feed my collection I like to make sure each snake takes the feeder and starts to eat before I leave the room. Then I give them some time and check to make sure everybody ate and I don't have a dead rat laying around to smell up the place.

The only snake I will throw a rat in and not worry about watching her start to eat it is my big Blood. She is a garage disposal and has never missed a meal. She has picked up plenty of others refusals though.