I think it's something along the 35 day line. At that point, the next highest ranking, active, member of the FC can take over. I would assume that the "active" party of that is the same as the leader, in that they'd just have to have been online within the last 35 days. In other words, the only way your friend will be able to take over is if all the members ranked higher have been inactive for just as long as the leader at this point.......