How long does it take a new season of a show to pop up on iTunes?

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In particular I am talking about "It's Always Sunny In Philadelphia", I've bought shows off iTunes before and they are usually out the day after the episode aired, but I have never tried to buy one the day after the season premiere. I missed it last night and I really want to see it (Actually I just want to buy a season pass) but it still isn't on iTunes and it has been almost 24 hours.

 

[Shorties]

Please, anyone know when its going to go up? I don't want to have to get this through other methods.