I would assume it depends on how fast your MOC informs the academy about their list of nominees. I got an LOA dated 16 October, got my nomination at the end ish of november, got a call from my nominating Senator's office saying that the Academy had informed them that they would be offering me an appointment in the second week of December. Got the official package in the mail on 23 Dec. hope that helps- but remember it is bound to vary among different MOCs. Congrats on fulfilling your requirements, though!