We like to work in trilogies. The story worlds and complicated characters we develop lend themselves to longer tales, but not the endless iterations that an ongoing series requires. Three novels is a generous amount of space to explore in and bring everything to a satisfying conclusion.
Many is the time we’ve bragged about our extensive outlining process, but even when you’re as thorough as we are in the preliminary stages you’ll probably find that things evolve during the actual writing. A lot can (and should) happen in 300,000 words, which is why we won’t publish the first book in a trilogy until the third one is written.
The dream would be for the entire triptych to be completely polished before any of it is released, just to guarantee that there are no more changes to be made, that there isn’t a single detail that could be improved. But that’s not possible. First of all because no manuscript is ever truly done. No matter how many times something is edited, there’s always a sentence that could be rephrased or a comma that could be added (or removed depending on which way the wind is blowing). The bigger issue though is that we don’t have all the time in the world. If we want to keep any momentum in our writing career, we need to release new work on a regular basis. And that means the first part most likely gets released before the third is completely done.
Emphasis on ‘completely.’
No matter how well-planned your story is, things will change during the writing. Maybe events will line up better if you adjust the timeline early on. Maybe a character who doesn’t appear until the third book will fit in more naturally if she’s alluded to in the first or second. Speaking of characters, once a characteristic gesture or phrase develops, it’s a good idea to sprinkle it in the early scenes to maintain consistency. Perhaps a minor character becomes much more important than you anticipated, and things will make more sense if their presence early on is enhanced. We sometimes discover that either Kent or Jen has an affinity for a certain character, which means they get to go back and punch things up in the other’s scenes. In the course of research you might discover a fun detail that needs to be present through the whole series. If the first book is already set in stone, it’s quite limiting.
For a satisfying and cohesive reader experience, treat your trilogy like one enormous manuscript for as long as possible.