I was going to say I don't like series that don't have a definitive "end", but then I remembered I'm a diehard of the Lincoln Lawyer series, so that's a boldfaced lie
in general I enjoy Michael Connelly's works.
I like series with definitive ends because I can follow characters over a long period, and watch them grow. And it feels fun to work towards an ending.
I admit I'm hesitent to pick up unfinished series unless it's guaranteed to end (e.g. the author has a good reputation for finishing books or the release date of the final book is imminent). I really don't want to read GoT or other notorious unfinished series and be left waiting for who knows how long to reach a conclusion. There's plenty of finished series for me to enjoy.
I will say series beyond 3 or 4 books are daunting... Maybe I'll learn to enjoy them? A bit scared to try
