This might be one of the easiest marketing tactics to follow that can ultimately dictate your strategy.
If you focus on topic clusters, it makes it really easy to understand how deep you can go on a topic to let Google know you're an expert.
If you don't have enough content to fill your clusters, that's a good indication your topic isn't big enough or you need to write more.
That's what I talk to Sean Halpin, of MJH Insurance, about as he tries to make sense of what he needs in his clusters.
P.S. A lot of topics get clustered inside the newsletter, you should come see for yourself.