I'm watching Zegapain at the moment and it's awesome, I'm only on the 13th episode and I'm hooked, kinda sad storyline though...
No you see why I recommended it, the storyline is totally outside of normal realms and thinks just keep bending in seemingly impossible angles.
InuYasha was probably the only Anime series I have seen that kept it going for so long (167 episodes I think plus 4 movies).
fair do there were 1 or 2 episode fillers from time to time, but like with Bleach you eventually catch up to the Manga Storyline.
When the anime reaches the current timeline of the manga series it can do one of two things;
1) End the Anime completely (Inuyasha), or
2) Put a whole bunch of fillers in and make a "arc/season" out of it (Bleach - Bunto Arc) so you can put the Manga story on hold for 40 episodes..
In all honesty I wish Inuyasha just took a 6 month break and then start up again..