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).