People somehow get attached too much with characters and they just refuse to let it go. I think it is not about that people like infinite series more than finite series. People like good shows (what constitutes good can differ for everyone ofcourse). It is just that the shows which have a large following in the beginning get dragged for years because of their diehard fans who just cannot accept that the show has to end. Just the presence of their favourite onscreen couple is enough to make them watch a show. So even if the track, story and the screenplay is absolute crap, the TRPs remain strong. And as long as the TRP remains good, the show is not going off air unless the CVs/actors themselves get tired of the show and want to do something different.
Look at the example of Yeh Hai Mohabbatein. In the beginning that show for me was just marvellous and it managed to get me hooked for some reason. But now it is totally unbearable. It has been dragging for a year and a half now with nonsense story. Many people (especially girls) are just obsessed over IshRa. And they continue to watch just because of the lead pair. The TRP is still decent and therefore show is going on. I am sure even if the show goes off air tomorrow, the fandom will start writing letters, petitions and emails to continue it.
Look at what happened to KRPKAB. I think they made a bold and commendable decision to end the show when they had nothing meaningful to show. And then what happened. They get bombarded with emails and requests from fans to continue the show. And in a matter of days, they decided to come back. It is unlikely that they have thought of any good story to tell in such a short time. But people don't care. They just want to see their favourite couple on screen. They hardly care about anything else.
Sadly, we haven't learnt to let things go for good. We become too obsessed.
--My two cents. Good luck for your research.
Cricket
Bade Achche Lagte Hain Naya Season
