Take 5 - Prelude to OBW

What is the difference between girls and woman aged 8, 18, 28, 38, 48, 58 and 68?

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!