Question about dead sims being culled

@Yoglooney 

Once a sim dies, there is a set time limit until the ghost is culled from the game.  I forget atm how long it is but eventually all ghosts will be culled.  You can extend that time if you use the Strengthen option on the urn or tombstone if you have it when it shows up.  It might take a while before the option appears though.  That will extend the time they will remain in the game.  You can do that repeatedly.  But, if the urn or tombstone is on a lot you are not playing, you may or may not get the wall pop up notice that they are fading away. 

If you use mods, the SimsInfo mod will tell you how long the ghost will hang around.  

The only way to keep a ghost in the game indefinitely is to make the ghost playable again by asking or inviting them to join the household.  Once you do that, you can move the ghost to its own household to free up a sim slot in their original household if you want to.  Since playable ghosts don't age, you can keep them in either tab in Manage Households.  For those that I want to keep around, that's what I do.  You can always release them to the Netherworld at any time after that if you have the urn or tombstone for them if you decide you don't want them in the game anymore.  Or you can bring them back to life by using Ambrosia, the book where you recorded their life, the Wishing Well or the Dedeathify spell if you have the packs that give those last 2 options.

Hope this helps.

There are mods that can prevent culling of sims in game also if you use mods that is (MCCC being one of them)