You should make the startup grind take longer to accomplish (increase store prices, make end portals event loot only etc.)
Add a base building contest (people need shit to do during downtime). Host a pvp competition with a monetary reward, "Map 8 MVP" forum flair, etc. (goes to fac with most event caps)
Maps don't last because ppl only care about the initial race to #1 fac (whoever caps Citadel). After that there is no more "race". Back in the day on og HCF, 1v1s/2v2s and were the second "race" - to being the best players. A 2v2 tournament would be good idea to have within the next few days after Citadel.