I find that when I think of something to write, that is when I write. Fortunately, I write really fast when I am in the zone so I can sometimes churn out a lengthy post, images and all in 30 minutes or so. There have been occasions where WORK demands require me to stop mid-posting, but I am fast enough that is not usually the case. So far I am fortunate enough that my stream of consciousness doesn't appear to be too bad when I write. So I can get away with it. I can tell you the more I do it, the faster I get, and the easier it becomes. So all I can say is WHEN it is calling to you, write. If you wait to write that seed may never germinate.