It just needs to be long enough to solve the whole problem so people can decide if they want you to help them. Of course, that might be an oversimplification of a slightly more complex problem, however, remains the majority of the solution. The length of your content isn't worth obsessing and over thinking, because the only thing that will come from that is not doing anything. That's why you have permission to start hitting publish anytime and build up to whatever number you're currently not hitting. That's what I talk to Taylor Garcia, of Jackson & Jackson Insurance, about his word count concerns.