What is the difference between girls / women aged: 8, 18, 28, 38, 48, 58, 68, and 78?

At 8: You take her to bed and tell her a story.
At 18: You tell her a story and take her to bed.
At 28: You don't need to tell her a story to take her to bed.
At 38: She tells you a story and takes you to bed.
At 48: She tells you a story to avoid going to bed.
At 58: You stay in bed to avoid her story.
At 68: If you take her to bed, that'll be a story!
At 78: What story? What bed? Who the hell are you?