It all depends on the game. Multiplayer-centic games like Battlefield can easily get away with releasing maps and modes for a game well over a year after release. It takes a special single player (or co-op) game to get away with that policy. But if you're going to do it and be successful you need an approach like Borderlands where you release the first content with a month or two after release and keep the content evenly spaced out.
Games like Bioshock Infinite and Last Of Us have really dropped the ball. Nine months to a year after the initial release of the game? Give me a break. A very small percentage of people are going to give a shit. While I was thoroughly unimpressed with Infinite and wouldn't have cared either way but I absolutely loved LOU and at this point I still don't care about the DLC that finally released today. I'm sure I'll get it when it goes on sale but had it released within three months of the game's release I would've been salivating over it. I understand why because a development team like Naughty Dog is sacrificing all of their resources on two games, LOU and Uncharted, so it probably isn't even possible to start work on DLC until after the main game is complete. Although, from what I hear, the LOU DLC is a pretty significant chunk of gameplay, more in line with "expansions" like the PC world has had for ages. Releasing a major expansion for a game in nine months seems pretty acceptable. Whereas you have the Burial At Sea expansion for Infinite, which appears it should've been ONE piece of content that they separated into TWO and is still only about three hours of gameplay, is not acceptable in my opinion.
There may be no real solution for teams like ND, which is unfortunate.