Complex (”plex”) spawn mechanics are governed by a few different factors.

General Spawn Rules

• Navy and Advanced plexes spawn at approximately a 2:1 ratio.
• On average, frontline systems will spawn ~6.5 plexes. This means that a frontline system with no activity would eventually have 6-7 plexes available, on average. Frontlines can have more or less depending on the spawn location of roaming complexes.

Respawn Timers

Complexes respawn on a timer. This means that when a plex is completed, a new one will respawn a set amount of time later.

• Frontlines: 20 minutes
• Command Operations: 40 minutes
• Rearguards: 60 minutes

Static vs Roaming Plexes

Only 2 sites (Small and Scout NVY-1s) are static sites and will respawn in the same system every time on a timer. Most (60+) complexes are roaming complexes, contributed to a roaming pool. These have a higher chance of spawning in a different system than you captured them in. Thus, if you are running plexes in only one system in uncontested timezones, you are limiting your progress to ~1% per hour instead of 2-5% or more.

This also means that you can purposely burn down timers of complexes in other systems, and leave them without capturing, if you are at a numerical disadvantage. This will slow the opposing side’s push.

Credit to @Aliventi for recording every frontline for 48 hours in 6 systems and re-watching it to understand this process deeply.

Changes as of August 1, 2023: https://www.eveonline.com/news/view/patch-notes-version-21-05

• Large and Medium NVY-1s added to pool of roaming complexes
• Ratio of NVY:ADV sites adjusted from ~3:1 to slightly below 2:1
• The number of -5 complex spawns was reduced (no exact number given)
• Overall quantity of complex spawns reduced by ~30%, from ~8.5 plexes per frontline system to ~6.5 per frontline system