SEO effectiveness depends greatly on the industry and region you are trying to penetrate. If the region you are marketing toward is saturated with your kind of product or service business then the process can be a long one. This results from the number of businesses that are bound to be optimizing their sites as well.
Take heart, however. With practically any businesses, you should see results within the first week to month. With steady work on your site’s SEO, you should see a steady rise in its relevance and status on the search engines.