Depending on how close the opposing strongholds are I usually burn all my fans eating up empty spots. I typically go around my main stronghold to ensure it's protected.
I also try to find bottlenecks in the map, meaning a single territory between strongholds. I will then split fans up between those territories. Not all my fans but enough to deter other teams from attacking them.
However, that will force the other strongholds to build up large amounts of fans closer to their strongholds. I wont usually wait to long before I power through to attack them.
Also, where the bottlenecks are, I will usually build up a second territory adjacent to the bottleneck. This way when I start moving through the enemy territories, I can counter attack them when the other team tries to come behind my first line.
I just realized I play this like a game of Risk.