and the fact that a lot of people can't play it for hours at a time due to real life getting in the way
So? That's what saves are for.
Anyway, I don't think he was asking about real-time realism....as in concurrent timelines being constantly tracked for all events in the game. For example, for every minute you waste on Illium not tracking down Thane, he gets closer to killing Nassana and then, say, leaving the world, unable to be recruited. I agree, that would probably require too much of a save file for the 4GB and arcade consoles (though probably not too much for a few-gigabyte USB stick).
But rather, a system based on when you start a mission or hit key moments. Like Admiral Hackett calls in with a side mission of rescuing some family from pirates. If you don't start that mission within 3 missions, it's too late, they're all dead. Or, going with the Thane example, if you talk to Sernya, she tells you he's started after Nassana and you better hurry, but you spend another couple hours (in Mass Effect time) dicking around at the vendors...too late, he's been killed by Nassana's forces.
Much as I love ME2, there really isn't much sense of urgency while you're building your team. There are few consequences for doing things in any random order, taking forever, etc... Until you get the Reaper IFF, and you're basically forced into doing the suicide mission after a small period of time/quests, leaving you a small window to get get any remaining loyalties (Side quests don't matter. You can always finish those after doing the mission).
It's certainly not a phenomenon unique to Mass Effect though. Most shit in the Elder Scrolls games isn't time sensitive either.