The never ending Series (Novel length)

IMHO 3 or 4 books
WOT, Foreigner,Dresden files ... and others that seem to be just one l-o-n-g story. Same main players in just another episode.
I do NOT oppose
Universe set stories : (but there are some)
Pern Books had various cycles that share a common theme and even touched some characters from the others:
Dragonriders
Harper Hall
Renegades
Liaden Universe has
cycles that revolve around the cycles main characters
Publishers succumb to Fan input (or the bean counters) and have the Author crank out another episode. At some point the well runs dry and the Author has not really grown new branches to explore
my 2 cents