Knowing when to quit is crucial to the longevity of a series. It can be argued that it is always better to have more of something you love, as the earlier and better episodes will still be there to enjoy. Even if the quality declines, whats the harm of it existing?

TV shows are not like movies, where it is relatively easy to separate something like "Die Hard" from "A Good Day to Die Hard" by just pretending the latter does not exist. With a new season, fans will always feel obliged to sit down and watch what happens next, to get the full story.

While each movie tends to have a clear beginning, middle, and end; that is nowhere near as well defined in a series. Even if season 5 of "Buffy the Vampire Slayer" closed on the perfect note, the existence of two more seasons makes it impossible to receive closure from it.

Here are three ongoing shows which are starting to unravel and should consider calling it quits, before hurting their legacy.

'House of Cards'

"house of cards" played an important role in establishing Netflix as a force to be reckoned with. Unfortunately, the series has been on a steady decline for a few years, with season 5 easily the worst. As Netflix announced another season, I genuinely hope this is the last.

We live in times of political turmoil, one ripe for social commentary, but "House of Cards" has run out of anything new to say.

The central couple is still fun to watch, but the characters that surround them have thrown off their magic. There is not a single real person, as every politician is in the game simply to get more power. Just because it is cynical does not make it a biting criticism of society. If anything, it is just a cliche.

'Arrow'

Season 5 saw "Arrow" return to form after the abysmal previous two seasons.

The show went from a cheesy but violent superhero drama to a soap opera centering on Felicity and her romance with Oliver. The tonal shift made no sense and nearly ruined the good work done in the first two seasons.

Season 6 would be a great point to cap the series. Hopefully, it manages to maintain the quality seen in the previous year, with a focus on Oliver and his new team.

This entry is not about putting it out of its misery, but rather ending "Arrow" on a positive note.

'The Big Bang Theory'

How is this still on the air? "The Big Bang Theory" was never a great show, but it had its moments. Somehow, eleven years later, it is still on the air. The laugh track is a dying breed, so maybe audiences are unwilling to let go of the last of its kind. With a Sheldon spin off on the way, it is time to put this outdated series to bed.