The amount of visitors coming from the paid traffic will dry up if there is no consistency in promotion to draw the traffic to the website. If you rank your website using the natural and organic techniques, it will be hard for your competitors to outdo your performance on the search engines. Because of the quality of your website, in terms of content, you will enjoy regular visitors all the time.
It's great to have a mix of paid and organic traffic but organic traffic is good for long term and building your long term audience.
But getting organic traffic without good keywords is hard. You need the right keywords that fit your brand and business.