Some people may think I’m too particular, but I prefer consistency in my fiction. If a writer describes a character as being one way, then describes the character as being a different way—without somehow showing or explaining the change—I’m knocked right out of the story. It’s the same way for settings. If you start as setting as being one way, and then change it without showing or explaining the change, your story will lack an important component of consistency. For me, the words we write create a strong semblance of reality that should be maintained over the course of a story, not discarded for the sake of convenience.
Most readers might not find such inconsistencies as disturbing as I do. Some readers may not even notice. But many readers are going to notice, at least unconsciously, and it’s going to interfere with their ability to suspend their disbelief through the course of your story. So, as a writer, you have an obligation to maintain consistency as best you can.
You can create tools for yourself to help you maintain this consistency. Create character and setting sheets for each of the people and places that will present themselves in your novel. This will provide you a ready resource you can include with your outline to help you produce consistent descriptions. You might not know all of your characters or all of your settings at the outset. The descriptions may change many times as you write, before you settle on a final look and feel for each person and place. That’s okay. Start with what you know and keep track of what you change or add. Be sure to have a final, official version of each sheet when you go through to make final revisions, and be sure to revise true to it.
It might be a bit tedious to create sheets for every character and every setting, but it’ll help in the long run.