The converse problem to this in US programmes, which I think House suffers from and Heroes was ruined by, is that of characters changing wildly in motivation and philosophy, with no in-story reason, from one episode to the next -- which I can only suspect is connected to the practice of generating the huge amount of screenwriting needed for a 22-episode series, by giving each individual episode to one writer from a large pool. (And, I suppose, by not having a powerful-enough script editor.) On most British 6-episode series, the same team of writers works together on each episode.

And where the lurches in characterisation aren't sudden enough to make the patchwork effect obvious, I'm sure it's easy to mistake them for an intentional character arc. As TS Eliot wrote, more people think it a work of art because they found it interesting, than find it interesting because it is a work of art. And he was writing about Hamlet, which, even if you televised the full text, gets all its character arcs done in much less time than a season of House.

Peter