As we continue to grow and learn the systems, one thing we have found that has helped us is to assign custom fields to spaces. This ensures the correct teams and people are able to see and tweak custom fields dependent on where it belongs. We found this as being helpful when various teams have been creating and update custom fields. By having it belong to a certain space has allowed for be more specifically tied to a space verses the entire account. Some people even don't share it to avoid possible changes from other team members.