This is indeed one of the most frequently asked questions. Organic or natural SEO is not an exact science. It is however a little predictable. A well optimized website with mild keyword competition should take no longer than 2-3 months before we start to see some of our chosen Key Phrases starting to rank in the top 30 listings.
If on the other hand there are a lot of websites competing for the same Keywords and Key Phrases it can take a little longer usually 3-8 months. The good news is once the primary keywords start ranking traffic to the website will begin to grow.