"On July 15, 2008, it was reported that FX has ordered 39 additional episodes of the series which means that the show will run until at least a seventh season"
I believe it is moderately successful, and it is definitely incredibly cheap to make, so it could go for a long while.
"There is a most absurd and audacious method of reasoning avowed by some bigots and enthusiasts, and through fear assented to by some wiser and better men; it is this. They argue against a fair discussion of popular prejudices, because, say they, tho' they would be found without any reasonable support, yet the discovery might be productive of the most dangerous consequences. Absurd and blasphemous notion."