It really doesn't matter who else did it and how long they kept it in the fermenter, what matters is that you are the one doing it this time and you will keep it in the fermenter until it is done. The time it takes can vary a lot because of variables like the temperature and the amount of yeast pitched, etc. and every ferment is different unless you can control all the possible variables.
While I have not done this particular beer, I have done a lot of Midwest kits and have never had a bad one. I've had very good luck just following their directions. Be at least as patient as their directions tell you to