How about in a 16V16 game? A 16 minute long cease-fire could prolong the game somewhat. Maybe they could go ALL economy with just enough millitary to fend off really quick rushes. Then, when you attack them at about the 12 minute mark, they start a 16 minute long building spree. If they went all economy early on, they could have an advantage in the inevitable end-game.
Also, the team could wait until late in the game and hoard their cease-fires. Then, when you have finally cornered their last fleeing villagers in some remote corner of the map, they start a 16 minute long barrage of cease-fires that you would have to wait through before you could finish them off and get the victory. It could be somewhat annoying.
How devestating could a 8 minute or 16 minute FimbulWinter be? It would hit all of your allies.