This is a complicated question to answer, since the results are based on so many factors, unique to your campaign and market. For a very general answer, between 4 to 8 months is considered fair for average campaigns using WhiteHat techniques.
The aim is to build the website’s popularity up naturally over time and create the conditions necessary for it rise organically in the search engine results. I advise all my clients that if they are looking for results sooner than 3 months, they are better off refraining from any SEO campaign.. There are hundreds of companies that will promise you results in this time, but you can guess the type of tactics they will employ to achieve this.. In most cases, it’s not ‘natural’ to rank this quickly and the procedure necessary to see results like this will almost always harm your site in the long run.. You may experience great results for a few months, but once the string starts to unravel, it can take just days before you’re standing there naked, with only one sleeve of your sweatshirt left and a whole lot of wool in a heap beside you..
To be blunt; slow, steady results last. Quick results fade. (In most cases).
Any good marketing company should have a well thought out action plan to be rolled out after results are achieved. Often referred to as ‘maintenance campaigns’, these aim to keep the current rankings where they are by sending continued positive signals toward the site and maintaining withstanding connections. Again, with BlackHat SEO this is rarely factored into the equation, since it is rare for a website to last this long when such techniques are employed and often ‘maintaining’ results is the last thing on the marketer’s mind ? simply achieving them is viewed as the goal.
You can estimate spending a fraction of the initial monthly cost of your campaign when in ‘maintenance mode’ since far less work needs to be done. The main reason for this further campaign is to show Google that you are still relevant and deserve the position you’ve been given. It’s a bad sign for a site to receive a lot of activity surrounding it, shoot to the top of the results and then go completely quiet. Google sees this as very unnatural. This is of course another benefit of WhiteHat campaigns, they are carried out in such as way as to stimulate real interaction in the first place, so a maintenance campaign furthers this work.