Thanks for your question, and please feel free to email us anytime, should you have more questions.
I have spoken with clients who have gotten a big boost and the job after just a couple hours, and others who have invested a full weekend or more. So it really varies by the individual.
In general, I encourage individuals to invest as much time as they can. The more you can "wow" your interviewer, the better your position to both land the job and earn a better starting salary.
I hope that helps, and feel free to reach out again.