Long Running Anime

Every now and then when trying to decide what anime to watch next I chose to watch a long anime (over 30 episodes)in many cases such as Death Note FMA and Naruto I do not regret the decision to spend so much time on them. However there are other times when I reach episode 20 or so I find my self wondering why i'm still watching, sure I enjoy the combat of Fairy tail and the comedy of Hayate No Gotoku and Gintama, but I feel no real desire to click that next episode button. Why what was that drove me to watch Death Note 4 times or keeps me watching every new Naruto episode?

Goals, the characters had clear achievable goals that I wanted to see them achieve not only that but everything in the main story worked towards those goals or added new ones e.g. Narutos rivalry with Sasuke constantly evolving, Ed and Al's constant hunt for the philosophers stone or Bakumans constant hurdles as Saiko and Takagi strive to create an anime worth manga.

The goals of Fairy, Hayate and Gintama are either very vague or non exsistant with the characters going from one adventure to another with no real purpose, such anime in my eyes survive soley on the strengths of the setting/world or a single character that people latch onto unfortunately for me I like a bit more substance to my anime , Bleach is an anomaly in the world of long running anime as despite there being a clear goal it is constantly moving or changing so it feels like the characters are make little to no progress no matter what happens for the record I have watched 200 episode of Bleach.

Of course there are other exceptions to this rule long running anime that I can enjoy that don't have strong objectives but the only one i have discovered so far is Hetalia and as much as i hate to say it that i primarily because the story are so disconnected i can easily pick any episode to watch and have it make perfect sense.