Hi,
First of all, I do not believe in SEO "experts", to me it's a scam business. But, I accept the idea I might be wrong.
However, I am curious. With all the fluctuations with the Google's SERP, I guess that among all the sites/businesses which hired SEO "experts" (employees dedicated to SEO, or hiring an external SEO company), lot are seeing their traffic decreasing or worse collapsing at each Google's core updates. So I wonder how these SEO guys are dealing with deceptive results and explaining this to their clients.