Keywords are very important in the ontinue doing link building for those keywords not as much as initially but keep doing it,Directory submission is best option in order to maintain and promote your keywordse are going for link building techniques like blogs, article, press release and many others,Its really a big part of SEO Job to maintain keywords at good ranking is just up to quality back link of your website and quality content on your website,You need to have a blog of some type and post at least once a week with related keywords in your post to show google your website is being updated with new content,Don't look at things as specific as keyword and concentrate on the traffic long tail and associated terms can be added to increase traffic overall so you are not relying solely on the terms.