Game length

[The Coil]

Got a question:

In an attack/defend QB, one of the key balancing factors is turn length. I think it is generally accepted that the longer the game, the more the attacker is favored.

My question: what do you consider a 'fair' game length in an attack/defend QB?

Obviously the other parameters matter as well, so assume a med. map, moderate trees, mod hills, village, non extreme weather/lighting conditions, variable ending. I'd be interested in anyone else's thoughts...