Any writer will probably tell you that one question people ask is, "Where do you get your ideas?" That along with, "How long did it take for you to write that?" are some of the ones that should be on every writer's FAQ list.
Where do my stories come from? Sometimes it's a phrase I hear or event I observe. Did that child informing his mother that she now needed to watch the baby because he was going to play with his friends say that because he has become the primary care giver or is it because he does he have an overdeveloped sense of "I'm the big brother and need to take care of him?" I can write a story from several perspectives in that moment: from the mother who finds it annoying and/or adorable he takes his duties as an older brother so seriously. I can write from the young boy's
perspective who doesn't understand why this is now his job. I can even tell the story from the baby's perspective the way Kurisawa did in Rashomon. The whole idea of personal recollection from the angle of perspective would work well in that situation, whether or not that's the story of that particular family.
Then there are the odd observations that trigger the imagination. Riding my bike home through an area of the neighborhood I normally don't travel through, something caught my eye at the base of a tree. There was a little door, complete with a fan-like window at the top of it that seemed to fit perfectly. I needed to take a closer look and noticed there was a little creature at the open panel at the bottom and a couple of frogs in a tub just beyond the door, on top of the roots. Were the frogs stranded there after a flood? Was this a friend they came to visit? Perhaps they were evil frogs that were finally confined by the tub. I don't know.
At least not yet.
But what a unique and unusual find in a neighborhood full of manicured lawns (and landscaping services to maintain them).
So to answer: where do stories come from? Here, there and everywhere.
To answer: how long does it take to write a story? As long as it takes (unless I'm under deadline, then whatever the deadline may be).
I have a feeling I'm going back to visit the tree to ask the characters there about their story this summer.