There's something to be said for discipline. An effective writer knows how to paint the scene, evoke emotions, make a point, and provide information all in the fewest possible words. You might find that amusing coming from me, since my stories tend to run around the 600,000 word mark. Just imagine how long those stories would be if I didn't edit them, and if I gave in to every whim and idea that crossed my mind. If you've read the previous blogs in this series, you'll know that I don't, because the same principles and guidelines that I use when I am deciding which story to tell apply when I am choosing which ideas, words, and scenes will stay in the story.
All that said, one of the most wonderful things about fanfiction from a writer's point of view is that generally (unless you're writing for voluntary challenge in a fandom community) your story can be as long as it needs to be. You don't have to worry about making it fit some publisher's guidelines for content or for length. For some folks, that may not be that big of a deal. Perhaps you are the kind of writer who can tell a complete story in 2500 or 5000 words, and you've never thought about writing longer ones. I have learned, though, that once you start planning a story for more than a 5000 word one-shot, you need to plan for your story to be longer than you think it will be.
One of my biggest frustrations as an author is trying to budget my time for stories that become longer and more complicated than I think they're going to be. The further I go along, the more I can see the story evolve and become more than I intended it to be. That means it takes longer for me to write, and I have a hard time answering questions about when things will be done or how many chapters here will be in the end. One of my writer friends calls verbosity my superpower. Sometimes I agree with her. Other times, I call it my curse.
Whether it's a meta-human gift or a form of karmic retribution, what I have learned is this: plan for the story to be at least half again as long as you think it will be. Budget your time by that estimate and plan your outlines or whatever other pre-writing that you use to account for the story to be longer and more complex than you have in mind. If you like to plan by word count and you think your story will run about 10,000 words, then estimate 15,000 or even 20,000. If you like to plan by chapters and you think the story will run 10 chapters, then estimate 15 or 20. If you have no idea when you get started, and you're just hoping that you'll be able to finish the story in a month then plan for two months or even four months. That way, when you got your enormous rough draft that is way longer than you thought it would be, you don't have to stress yourself out over it. You can edit the 20,000 word document mercilessly until you end up with a story that you're satisfied with.
On the flip side of this, I have also learned that there is a balance between giving the story room to grow and maintaining your control as the author. You can tell a story with a lot fewer words than you think you need, but if you allow the story to grow first and then trim it, you'll save yourself a lot of headaches in the long run. Remember that you don't need to show every detail, and you don't need to tell every person's story in its entirety. Write what you need to and imply the rest. You can always tell side stories or write missing scenes after the fact. It's important keep your focus on the story that you were trying to tell in the first place, because that's the story that your readers clicked the link for.