I want to answer this as a romance author whose current story is well on its way to be longer than 20 episodes…by far. 
I really think it depends. While there are definitely authors who will drag stories on to have more episodes and therefore more reads some stories simply need more episodes to get across what they need to tell. My story for example was only supposed to be around 15 episodes but due to some subplots I’ve added in and new plot points I now know that 15 episodes would make that story incredibly rushed and therefore not a good story.