I'm fine with 1 'expansion' per year. As others have said, too many takes away from the whole LCG concept.
Ideally, what separates an 'expansion' from a normal chapter pack, is that it includes 7 plots, & multiples of certain cards (maybe a new resource location, or some nuetral location or attachment removal/nuetering or draw that is fairly expensive compared to existing or in house options), and the deck would be playable (though wouldn't have to be competetive - so each house could still get 1-2 house specific cards that could be pulled out or pay gold penalty for, along with nuetrals & 1-2 dual-house cards).
While I'd like to see Tyrell, Arryn, and Tully be their own houses, if they are not, they, along with sub-houses or other themes (tourny of the hand?) are good fodder for the expansions.
I personally am not a fan of most of the extras we've seen so far (game board, title 'figurines', cardboard counters in core set & resin house card in Greyjoy). However, since FFG seems intent on adding something 'special' to these - I'd suggest card sleeves (Tyrell House if they are a future expansion, or other featured artwork), or a playmat that depicts a map of Westeros.