The realistic time frame I will say speaking from experience, depends on you. Why do I say that? You have to know your stuff to the point that you can teach it. Make sure what you are using for the CPNE exam (course guide) from Excelsior you follow it religiously, step by step. I did not go to any prep classes. All I did was set up my own clinical simulation, and practice! practice! practice! There are a lot of videos on you tube as well that can help you set up your simulation. You will pass!!!!!