I spoke to admins from other servers and they had been deleting npcs from their server every few days........ with 11 people on my server I had over 9000 npcs in just 2 days........ after the last update this now appears to have been fixed..... but today I also restricted number of npcs in the config just in case 100 people do log onto my server all at the same time lol
i find limiting the number of npcs can lead to an empty world when exploring new areas. with what you have done to your server (the db changes), and i think the npc spawns are on the server only you could just shorten their life i believe its in seconds. looking at the db -1 is infinite life(adult npcs for the most part). the ones with the assigned times(for the most part) are infant variants that trigger the ontransform event(infant to adult) ? you could possibly change the lifetimes for adult to say 7200(20ish hours). then in the config lower the re spawn times. this would give you a limited amount of npcs but keep them spread out.
EDIT: yahwho sorry just noticed what thread this was in. didnt mean to take it over