While search engines may change often, SEO does not. What really changes when algorithms are updated, either in tweaks or larger changes? The answer can vary but the advice rarely changes.
Create great content. Build quality links.
These two things will never change. Think you will ever hear the recommendation to an algorithm update be: scrape some content or your content isn’t important any more, just throw anything up. No. You will always want to have exceptional, unique content on your site. While on page factors might be decreasing in importance, it doesn’t mean that you would want to try and rank crap. Content is the foundation of your site; it will always be critical to your optimization, regardless of how important on page factors are.
Build quality links. When was the last time when there was an algorithm update and the SEO community decided the new tactic to help you rank would be to go create a bunch of spammy links? I think the answer is not in a long time. And I don’t think that will ever be the answer going forward. Getting links from reputable sites that are related to your site will help improve your ranking. This isn’t going to change. You will always want reputable people to endorse your site (even if it is nofollowed).
While there have been changes that effected link building strategies such as the increasing importance of having links from a large group of domains, this didn’t change the fact that you want high quality, relevant links. Sure, sites like Twitter come along and force Google to adapt their model, but it is still has got to be better to get a link from a well established Twitter users than someone who just created an account. Search engines will evolve, but content and links will be critical to ranking your content for the foreseeable future.
Writing killer content and building links that are from related quality sites are what I call sustainable SEO. While there may be gimmicks that gain you an advantage in the short term, focusing your efforts on sustainable SEO will help to ensure that your time is well spent in the face of future changes to search engine algorithms.