I never quite understood why so many long running anime series had so many filler episodes. The cost and work of the animation wouldn't be too different as far as I could tell. It's as if they all don't have enough plot to fill the number of episodes they want to make. It isn't that hard to come up with a feasible plot that would at least be more interesting than brain-numbing fillers. At the very least, they could make some of the fillers into episodes that develop the character a bit more. Developing the character's relationships with each other would help keep my interest anyways.
I mean, think back on the last 10 episodes of Shippuuden: How far has the plot developed? How far has the character developed? What has actually happened?! Nearly nothing, they could have fit it all into probably 2 episodes. In the last episode, the fight was supposed to be settled in 3 minutes before Sakura's poisoning set it. Something like 15 minutes after we were told this, Sakura makes some comment saying that a minute has already gone by. Most useless, distorted sense of time ever...
I think I'm working myself up now :p. It's VERY unusual for me to stop watching a series partway through (especially after nearly 250 eps, I'm usually comitted) but I think I'll have to give up on this series soon. Maybe I'll watch the rest in a few years when its done. Play it back at 300% speed or something, heh.