The thing to take note of is that standard episode times exist to make TV channel scheduling simpler. There's no equivalent of that in games, so why should designers worry about standard times?
It's not like standard times improve the experience. Look at movies; they pick whatever duration they like, just bearing in mind their customer has expectations that they'll get their moneys' worth and probably don't want to sit in a room for five hours, and because the producers probably couldn't afford to gamble with the cost of even more footage.
Okay, so it's a factWe know gamers will only play a given game for so many total hours. That'sWe are those gamers. However that's not a function of the time itself thoughwe spent, we didn't look at our watch, notice we'd chalked up ten hours total on Mario and suddenly ceased to enjoy it. That'sWe stopped enjoying a function of the player'sgame because our relationship to the game's experience changed over time: it no longer had anything we enjoyed. It became too easy or predictable, for instance. Difficulty is a large contributor to how long a player stickswill stick around: too easy and predictable, or unforgivingly difficult, and you won't try to go further.
In movies you'll get tired after five hours because you want to be elsewhere. The solution in games? Saving. There, another problem we don't suffer from: games can last for more than one sitting now.