There is no set time period for consular officials to set up an interview. It depends upon the current number of pending cases. It may depend upon the documentation in your file, which is always subject to review. You will know when you get the notice and are asked to seek a medical exam, among other items.
If six months pass, then you may want to hire an experienced immigration attorney to conduct a formal inquiry. You may contact the Embassy's Immigration Visa Unit in Casablanca at your own risk. It is very important to use exceptional care and treat consular officials with respect. This is due to the control that officials have over cases; some are under a quite a bit of stress due to under staffing of those offices.
The above is general information, not legal advice, and does not create an attorney client relationship.
It can take up to 6 months to get an interview in Morocco. It usually takes less. The NVC will send you a notice of the interview date, usually about 6 weeks prior to the interview.