All I can add (for Camp Horizon attack) is that a NPC with a Chocobo will appear at 14:27 on the map, to the west of the moutain, right north of the camp. Talk to her to register to the event, waves of Imperial Soldiers and wolves will then appear coming from the west.

They indeed give no exp/sp but they can drop +3 gears, got a Canvas Dalmatica +3 yesterday.

At the end, a coffer spawns where the NPC was and gives Deaspected Crystals (I usually get 5~8). It also unlocks an achievement on the Lodestone the first time you do it.

I am still trying to find out if there is a timer involved but for now it seems random to me, definitely less that 41~46 hours though. It happened again after 28 hours yesterday for example.