A year is a whole lot longer than a month. Also, CoD (which I'm assuming you're referring to, since nobody else really does that) didn't try selling the DLC before it was fully available, like Destiny is doing. This is a shitty business practice, and can hardly be compared to anything previously done.
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What about GTA IV? It got two large chunks of DLC for Xbox 360 for over a year before it landed on Sony. What's the difference?
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Because with that, technical difficulties made it impossible to release on time (in a form they were satisfied with). Not to mention that that wasn't a game with a large multiplayer community, while this is.