Nothing is ever done when it comes to Search Engine Optimization because the industry is constantly changing. There are always new opportunities. Websites require maintenance, and it takes work to remain at the top of the rankings.
It is entirely up to you, your business plan, and your financial situation. There are companies that charge upwards of $1500 per month, just to manage a site’s SEO on an ongoing basis. For most people this is overkill. Zee Designs will be happy to refer you if you require this level of special care.