I'm sorry, but there is no reason that a show should take that long, and I'm as patient as the next person. How long did Avatar: LOK take to come out after Avatar: TLA?
Not to compare apples and oranges, but YJ, Star Wars, Batman: TAS, and even lesser shows though still good JL/JLU, and Batman: TB&B all did not take nearly as long as LOK. YJ has had a great story arc and so did Batman: TAS (although it was more episodic than serial) were still compelling and entertaining.
LOK needs to return by Jan or Feb at the latest, especially if there isn't any marketing, merchandising, etc as with TLA so that it doesn't loose its attraction and viewers forget or grow out of it.
Just my two cents maybe I'm just going through withdrawals lol.