One of those guesses is that people are worried that the series will go on indefinitely.
Rest assured, that is most definitely NOT the case. I have a whole arc planned for the series with room to spare. I just ask that you have patience and stick with it.
I am planning on four books per year for the next several years, for an expected total of around 24 books, give or take a few. Yes, that's a lot of books, but they are short novels. Each has its own plot that wraps up in each book but that also contributes to the overall arc of the series in at least some small way.
My plan is to allow room for some meandering and lighter stories early in the series while continuing on the main story. Throughout the series, the characters will have room to develop in ways I can't even predict. The closer I get to the end, the tighter and more focused the stories will become in the main plot of the series. I have it outlined so that I know what points I need to hit for it to all come together in a nice wrap up at the end.
So, if this is your reason for not continuing, please be assured that this isn't going to be an always meandering, never-ending quest. I have a plan. It will come to a satisfying conclusion.
Stick with it. The best is yet to come!