Anime series' always vary wildly when it comes to length. Some shows are just a few episodes long, like FLCL. That series only clocks in at 6 episodes, but what a sweet 6 episodes they are! Other shows like Bleach are 350+ episodes strong with no end in sight. When you jump into an anime, sometimes you have to be willing to go for the long haul!
I don't know about you, but sometimes it takes a lot to keep me interested in an anime. I don't think it's too much to ask for when I want good characters, an interesting story arc and beautiful animation. Usually most anime provides that kind of content from start to finish, but some falter along the way.
Then there's the dreaded filler episodes that some series' sneak in there. There's nothing more annoying with anime than watching a handful of episodes that end up having nothing to do with the series' main storyline. You could take those episodes out and they'd never impact the story at all. That's the kind of stuff that really irks me.
With all this said, what's the furthest you've made it into an anime, only to poop out and not watch the entire thing? How long have you stuck with a series, only to give up with it towards the end? I know some people that have gotten within 5 episodes of a series' ending, only to walk away from it. Are you one of those people?