Painting is a great analogy and determining when a job is done. As with most things in business, it's an art form. Will one coat of paint adequately cover the wall? Great. Stop at one coat. However, when the job clearly requires two coats, never stop at one. If you notice, others certainly will. There's a balance between inadequacy and perfection. Finding that balance between one and two coats of paint will prevent you from consistently skewing to either side of that spectrum.