Cut up your game in "time pieces"

Recently I played more games on my iPhone than on any other platforms. Realizing this frightening fact -I'm a gamer, please understand me- I started asking myself why I was relying this much on my iPhone games. I started to figure out when and why I was playing my iPhone games. And as you might have guessed my conclusion was mostly time related.

First I realized that I played iPhone game in places or at moments I almost never played before : waiting for someone in a public place, in my bed just before sleeping, during TV ads, walking to the subway station, before the movie in theater, etc.
Asking myself why I was playing in those situations was pretty obvious, I had small time to kill, very small time to kill. The kind of time my Nintendo DS or PSP can't kill for many reasons : I don't have any of them always in my pocket, they're too slow to boot, their games are not made to kill this kind of time, I don't carry a dozen of cartridges or UMD anywhere with me, I can't buy a new game anywhere and anywhen, etc.

Then I take a look at iPhone games charts and, as expected, the vast majority of successful game (sales are a special case) are designed to allow short play session : Angry Birds, Bejeweled, Tetris, Doodle Jump, Flight Control ...

So it's a whole new world for games, a world that started with flash games played at coffee time and now expending to every small moments we often lost doing nothing.
Well, aiming to "short play session game" while making an iPhone games seems to be one way to success. But what about "play session duration" for other platforms and products ?

I'm convinced that well crafted (game) experience is bound to a good management of the time consumer has to offer.
I mean that games should help player managing their leisure time by cutting the game down to many layers of timed gameplay loop. Why I think it is so important to me and many others ? Because when I start to play a game (or any entertainment) I like to know if it will fit in my schedule and when I could stop playing without being frustrated or lose my progression.
(Talking about entertainment, look at the success of TV shows, 45 minutes session instead of 1h30 for a movie. I bet that's one part of their success)

As an example I'll take a game I'm currently playing : Alpha Protocol. First because it's fresh in my mind and second because those layers I spoke of are easy to spot and understand in this game.

Alpha Protocol cut up time this way :

A Checkpoint takes less than five minutes to complete, a Mission a maximum average of an hour, an Objective is about 5 missions and so approximately 5 hours, and a Game Acts is nearly 3 objectives approaching a duration of nearly 15 hours. I voluntary extrapolate on some durations but it gives you a good view of how the game cut down its gameplay sessions.

The way Alpha Protocol is divided help player to manage her goals and schedule easily for each play session which is a great advantage. In fact the player knows she could start a 5 minutes play session or a lot more if she likes it or has more time.

Moreover this way of cutting up gameplay could help the game to reach numerous design objectives as a well balanced reward system, game pace, puzzle complexity, quest design, etc.

In summary I think that dividing a game with a "time knife" adapted to its target expectations and free time is something that should not be underestimated.