GDAM: Single Play Sessions

I've submitted the topic for this month's, well, Game Design Aspect of the Month. Allow me to quote myself from the GDAM blog:

Games are designed with the understanding that each player needs to meet some requirements to get the best play experience. Hardware specifications and age or maturity level, for example, are even listed on the box. But game design also makes implicit assumptions about a less obvious requirement – the time commitment we ask from our players each time they sit down to play.

This is an interesting topic, I think, from both a traditional game design point of view and from a pervasive/transmedia point of view. Like the sand of time, the social contract between a player and a designer is always shifting. 

GDAM is now actively soliciting contributions talking about this topic, and I'd really love to hear what all of you smart people have to say. If you have an opinion or theory on the matter, why don't you write it down and submit it?