Define a schema for any bespoke configuration, it's not too hard. It's needed to make it translatable, but Drupal 8 will also validate your config against it so it's still handy on non-translatable sites. As a schema ensures your configuration is valid, your code, or Drupal itself, can trip up without one. Set up a schema and you avoid those problems, and get robust validation for free. Hopefully my example YAML shows how it can be quite simple to do.
