If it's a 4v4 or 5v5 on faster settings, give yourself at least 3 hours...the game probably won't take much longer than 2, but you never know, and you don't know how long you may sit in the lobby waiting for TickleDick and BitchPants to stop bickering about who gets to be team captain....
If you're doing comp stomps, allow more time...for one, you'll see more lower skill players who have to entrench or really push things to late game before they can break through an AI...also, it is etiquette to generally quit as a team when it is obvious your team cannot win...this prevents hours of mopping out after a team has essentially already won...hence, human games end faster than comp stomps...
If the game speeds are fast or normal, allow more time....
If you're doing 1v1, it's a crap shoot...sometimes these games are decided very fast, and sometimes they can go on for hours because each player entrenches with roughly the same amount of stuff...
I don't think you're going to see too many ICO games, even the normal speed ones, going much longer than 4 or 5 hours...and like I said, competitive 4v4s and 5v5s rarely go more than 2 hours....
No version of Sins had a campaign...
