Forty is the line of demarcation that says you're an adult now. You're an adult, so don't pretend you're a kid anymore.
Then came the choreography... the impact of music and choreography tends to really emphasize an overall feeling of what you really want out of the program.
I've seen novels that have grown out of one story in a collection. But it hasn't occurred to me to take any of those stories and build on them. They seem very finished for me, so I don't feel like going back and dredging them up.