it's your sister Cheryl!
I work for Petersen Games. AMA
I'm looking at putting together some games for a convention next month, and I had some questions about OMD. How long does it take to teach the game, and how long for a 4 vs 4?
I'm thinking I'll have two people handling the setup, do a pair of warmup games, and then a combined 4 vs 4. I've got 4 hour blocks to work with on the schedule, which should be plenty of time for a learning game and then a rivalry game.
With a full group of 8 players it can take anywhere from 90 minutes to a few hours. Normally for co-op I estimate 20-30 minutes per player (so a four player co-op would be about an hour and a half to two hours).
However, with Rivalry the game sometimes ends earlier than you think - because one team can get an edge and kill your rift faster than you expect. At other times it takes 2-3 hours (or more) because there's 8 people each agonizing over their turn.