The other factor is that some shows start in midseason slots. The Unit, which Bravo somehow have the rights to, stayed in midseason for its second season in the US meaning it didn't start showing new episodes until the Spring.
24 effectively follows the same model though it starts a little earlier.
I'm waiting to see who, if anyone, brings Dexter to Irish terrestrial/basic cable screens. It's a Showtime series, which would make Channel 6 the favourites to do so. It will air on FX (which I can't get) from July.
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