The key question here echoing Paul's comments is 'Why are seasons so long in American shows?' I mean, even when you look away from shows like sitcoms which often have 20+ episodes a season to dramas like Dexter or Sons Of Anarchy (tbf, I love both and always want more) having 12 episodes in a season, if not 16 - 18 even is a little much. With UK shows it can be as few as 3 hour long episodes per season, a longer season will engender 6 - 9 episodes.

I think America's missing the fact that too much of a good thing, can be worse than less. Something I think that British TV with exception of it's huge pantheon of soaps which are now shown 5 - 7 days a week with casts which are and do interchange at times, has done correctly.