SEO is a continuous process, and you shouldn't stop link building once you achieved your desired rankings. As there are many competitors who are targeting same keywords like yours so if you stop then you would be easily outranked. You should continue to build your links so that you can stay ahead form your competitors and maintain your current rankings.
While building links we always monitor the IPs of the websites from which we produce content, and slowly and cautiously produce content that is organic, valuable to the web and will increase your ranking.
