Asking when your SEO campaign is completed is a bit like asking when road construction in your city is finished. Roads need repaired and maintained, new shopping and housing developments pop up, more efficient traffic options need to be created. The construction is never done. Just like the Search Engine Optimization of your site.

Here is why:

1. Search changes. If your site was perfectly optimized for Google last year at this time and you haven't touched it since, that means that your site was last SEO'd before Google rolled out social search, the Wonder Wheel, and enhanced Places Pages. Oh, and Google Instant, which when paired with Google Suggest probably changed the keyword phrases your target market uses.

Oh wait, the combination of social, local, personal and universal search means that I may get results that include a video for the Indian restaurant in Columbus that my cousin who I'm connected to via LinkedIn tweets about. But you will never see that video in your search results. And there was Google Caffeine. Oh, and Yahoo! and MSN went from "also rans" to a combined force that could be driving 20-30% of your search traffic. So yes, a few things have changed.

2. Your competitors change. Let's say your SEO program went great and you increased sales 20%. Unless you are in an industry that is growing a lot, that means somebody lost sales to you. So what are they doing? Upping their SEO game with more links and more content to compete against you. When you dominate search, your competitors all come after you.

3. Your search terms change. This is probably the biggest mistake we see organizations make: Say a company offers roofing repair in Denver. The marketing guy says "We need to focus everything we have on the phrase 'roofing company Denver'." After some research we find that there are 400 ways people search for roofing companies in Denver. Like "Denver's best roofer", "find cheap roofer Denver" and "Denver roofer accepts xyz insurance". We target some of these phrases and then we are done, right? Wrong.

The next day The Denver Post runs a story about energy efficiency. Suddenly search volume on the term "energy efficient roofs in Denver" jumps. Then there is a hail storm and search volume now jumps on "Denver roofer hail damage." Then, two weeks later, Congress announces that the government will offer tax credits to people who invest in their homes this tax year. And now the fine citizens of Denver start searching on "roofing tax credit."

One of our clients used to optimize on terms related to "swine flu." Overnight, it became "H1N1." Another client earned a spot on Oprah. Immediately after the show aired people started searching on his services plus the term "Oprah." The meanings of words change too. "Short sale" used to be what Old Navy had when it offered discounts on pants that end above the knee. Then it meant buying a stock at 8 am and selling it at noon. Then it meant what you did to avoid foreclosure on your house. The people within your company may always call your products and services the same thing, but the rest of the world changes terminology more frequently than you would believe.

4. Your prospects change. Let's say you have a revolutionary way to treat diabetes. You work for six months on your SEO program and reach a lot of new patients. Then you stop your efforts. On the first day of month seven someone is going to be diagnosed with diabetes and will be out searching for treatment options. Stopping your SEO efforts is like saying you're going to have a sales team for six months and then fire them all.

With these examples, you will find that your SEO campaign never truly ends. You must continue adapting to trends and shifts in search terms. Your competitors won't stop trying to catch up with you, so that's why you should never truly consider your SEO project finished.