It's more a case of, "why are they still going on?"
I love them but it's exhausting to continuously follow both of them (and watch one of them). Good things eventually have to come to an end

. I just read the latest chapters, both pleased me, but one of them suggested just how much longer they intend to go on.
On another note, I'm struggling to decide if I should watch Death Note or Bakemonogatari 1st...