Letting An Idea Sit

    It's awesome when you come up with an idea for a new story. And sometimes it's a chain reaction: you get an idea for a character, then a setting, then other characters, then a villain, then a story plot (or in completely different order). And when those ideas do strike, the characters seem awesome, the plot sounds easy to write about, and you may want to start writing the first draft immediately.
    Although, you might want to wait a few days or so first. Let the idea sit in your mind for a while.
    Doing so can give the idea some time to mature a bit, time to solidify the characters and the plot in your mind. You may also come up with some crucial details to add to the story, saving serious re-writing time. Also, in waiting a little while, when the initial excitement fades a bit, it can be a lot easier to focus on writing one chapter at a time (you know, instead of trying to write your way through a hurricane of what-ifs that pop up whenever you think of the story).
    How long do you usually wait before beginning a first draft?