My three year old daughter has been in her own bed for about a year now. In all that time she has never once gotten out on her own. She’ll dangle off the edge to try to grab something from the table next to her, or peek over the end to see the toy she dropped on the floor, but no matter how long we leave her there she stays in bed. She even has a step stool to get in and, theoretically, out. It’s not like she doesn’t break other rules. Come to think of it, I don’t know that we’ve ever told her that she’s supposed to stay in the bed.