Stuff will pop up, before, during, and long after publication. I know I constantly pick at our first three books, and I do find things that I could add, but there comes a point where we need to put the manuscript down and move on to the next thing.The nerve, putting off a war for 75 years.
Yep...no weathertops.
That's one thing that vexes me. I am writing book three, and something comes up that makes me go...Oh, I need to add that in book one. How can I publish book one, when stuff may pop up that makes me want to add more detail? I dont know.
And then leave it alone.
When these thoughts pop up, make note of them so you don't lose them, and then decide if the new information is really crucial or not. Series length is going to have an impact here. We're working on a long-running series, so we have more wiggle room to add to our worldbuilding and metaplot. A trilogy needs to be more contained. You can write a trilogy in one shot and have all your details in order before you publish. With a long-running series things can and do change. The only thing to be done is to build on what you've already written and keep moving forward.