Any long tedious series worth reading?

I've stayed away from most series that go on indefinitely, but are there any worth trudging through?  This includes licensed drivel such as D&D, Battletech, Shadowrun, MTG, Battlemage, Warhammer, Dr Who, Xena, Buffy, Marvel or DC based novels, Star Trek, Star Wars, and any series which exists to promote future sequels (including Harry Potter, Wheel of Time, etc).

"A Prince of Darkness" by R. Scott Bakker, is a good trilogy, with another set in the same world starting up, witht he first being released next year sometime.  (It is a good read, for the author's first real set of novels, and should only get better from here.)