Like Apostle Jack, I've been writing since I learned how to hold a crayon. I used to write little stories - or scribbled them and my mother read them to me.
By school I would write anything I could. I would write short books - with chapters.
I wrote creatively. I wrote journalisticly, I wrote plays.
Now I'm in the midst of a story which has held me up while I wait for the characters tell me what they're going to do next.
I guess I "overanswered" your question. I guess the short version of my answer should be:
"All my life."