It took 20 days for me to receive the GCMS notes.
I would recommend ordering them now. There is no need to order multiple, especially for a Study permit application. Since you got AIP, go ahead and order it, it most likely means that a Visa Officer has reviewed your application and left some notes. It would also help to have a complete application, that way you know they have everything and are making decisions based on that.
The GCMS notes aren't generated on the day you order them, Mine was generated 1.5 weeks after ordering it, other people around 3-5 days, so it depends.