Yes! Search engines are constantly changing and updating their algorithms, so as a result, SEO best practices are constantly evolving.
SEO-friendly practices of 2004 are dramatically different from the best practices of 2014 and the sites that ranked on page 1 of the search results in 2004 may now rank on page 101.
Therefore, you must improve your site in accordance with the most up-to-date criteria. Many SEO agencies use outdated (and outright harmful) practices, so it’s essential to turn to an experienced agency that goes the extra mile to stay on top of all the latest search engine algorithm changes and SEO best practices.
Using outdated SEO practices can be more harmful than ignoring SEO entirely.