How long does SEO take to start working?

So your website doesn't show up well in Google, and you've hired an SEO firm to help fix that. You're paying them the big bucks, perhaps thousands a month. But you've been paying them for several months now and haven't yet seen any increase in website traffic or business.
Should you be worried?

The post How long does SEO take to start working? appeared first on T&S Online Marketing.