Yesterday, when I was looking for a next book to read I found the third and final part of the trilogy I remember reading years ago. I remember having to wait for the second book for a long time and after that this third one. I actually gave up waiting for it. Too many times that has turned out to be indefinitely.
Some authors do write consistently when it comes to the series of books. You can (almost) always trust them to deliver the next book on schedule. Sure, sometimes these authors don't have end in sight and they just keep writing new books to the series.
But then there are authors that seem to take forever to complete their story. When (if) the conclusion comes it has been too many years to remember where the story was heading. In the recent years I have been trying to avoid these unfinished tales and prefer picking up finished series or even stand alone books (which there are way too few available).