Should businesses do SEO if they already rank?

Absolutely! SEO is dynamic. Search rankings and results shift and change. What works today, may not tomorrow. Google is constantly updating and refining its algorithms. Also, as competition increases it’s important to stay on top of SEO so your website continues to be relevant. Good business websites are doing SEO constantly to maintain and continue improving their rankings. You may rank for your core terms, but it’s important to rank for secondary and tertiary terms as well.