I have used a portfolio type website since 2003 for my work and experimented with dozens of designs and several SEO setups/ configurations. In 10 years of business I see about 5 jobs a year come in on average as a result of the website. My biggest jobs in fact were from clients who found me in a search. All in all I would say that over the span of time keeping my site updated (code-wise and content-wise) and SEO "conscious" has been very much worth the effort. Especially comsidering that I have yet to use social media tools as a means to attract potential clientele. I should state here that I am established freelance photographer who relies heavily on direct introductions and occasional bouts of cold calling and knocking on doors of potentials with my portfolio in hand. If I relied solely on the website to grow my client base I would have been out of business long ago.