Just because you are getting good search results now does not mean you will continue getting good search results. Your success might have to do, not with your own ingenuity, but with the laziness and/or ignorance of your competitors. If your competitors are ignorant of SEO, or are unaware of its importance, this may be one of the sole causes of your superior search engine rank.
It is therefore important that you practice SEO even if you already have such a presence. You never know when one of your competitors will wise up and decide to learn and practice SEO or higher an SEO practitioner to get the job done. He may be doing superior in areas in which your flagging, and it might be the addition of SEO to his repertoire that puts him out on top.
Keep in mind that a high search engine ranking does not necessarily indicate popularity. You may be ranking high on a search engine simply because of you have your links plastered all over internet forums and blogs, which, as we have seen before, tends to increase one’s search engine ranking. Of course, this (as well as other) means of SEO practice is likely to increase your popularity to some degree, but it is not itself an indicator of your popularity.
Remember that you are not simply trying to get keep to visit your site. You are trying to get people to visit every page of your site. Rather than thinking of your website as one, indivisible, monolithic entity, it may help to think of it as consisting of several subsites rather than merely constituent pages. I myself have tons of different pages on all sorts of subjects on my website, so I try to obtain search engine and traffic eminence for each of these pages as separate units, dominating several popular, though unrelated fields and their relevant keywords.
Keep in mind also that ranking #1 is not everything. You may be ranking #1 for a keyword or key phrase for which virtually no one searches. Indeed, this may be the sole or only reason you are search engine ranking so high. No one else is using such a keyword or key phrase on their website or in their SEO practice, and it should therefore come as no surprise that you are ranking number 1 in this keyword or key phrase or term.
Of course, this also means that no one is actually searching for this keyword or phrase or term, and so your #1 search engine rank is in this case irrelevant. Success in search engine presence has to do with ranking high for a commonly searched for keyword or term or phrase, not high search engine rank in and of itself.