What does the last stanza in Cinderella mean?

"never telling the same story twice
never getting a middle-aged spread
their darling smiles pasted on for eternity.
Regular Bobbsey Twins.
That story."

The stanza is a hope of what we wish life to be. According to Michael P. Weinstein, the Bobbsey Twins were in a book series of which these two twins, Bert and Nan, have many adventures. The series would last 72 books of adventures. However, through out the many journies they take, they never age. I believe Sexton is glooming up the image of the happily ever after we all love. I believe she's saying that we can't believe that life is a fairy tale, marriage is not always easy. Moreover, Sexton is implying that people will age unlike the Bobbsey Twins and when we do life won't be all smiles. However, even though all our lives are to end, it's our story and we still decide how we end it.