"The idea of this was to create a map that would be stable across days and/or weeks. Our longest map operation was creating a base, as part of Operation Green Field, and lasted over seven days."
you kept a map/server/op on for a week how the heck you manage that, did you make the map as big as europe lol?
The map would spawn things, and remove them, as they were not needed. For example, 10 C130's were available for use, but unless you had gone to Air Command and signed one out - there were none on the map... simply a variable on the server telling it that 10 C130's were available. If you signed one out, it would know 9 were available, and if you returned it - back to 10... and so on.
The same went for enemy. Occasionally enemy would be spawned to attack bases, and once they had succeeded/failed - they would be removed.
The mission in Operation GREEN FIELD was to barricade the city Bangango and defend it from an enemy. It took a few days to build the defenses, and then we held it for several more. The enemy didn't attack when there were no players on the server.