When this is countdown is at 14 days the gravestone will get a new interaction called 'Strengthen Connection to the Physical World'.

There is a countdown on the graves 90 days(hidden game mechanic).

Housed dead sims will now spawn an urn or a gravestone even on an unplayed lot, even if they are NPC's you've never played and even if you are not on the lot when they die.

Ghosts will now no longer disappear from family trees when they are returned to the netherworld or culled by the game.

Dead sims need to be moved back into 'My households' to be protected as dead sims are automatically unfavorited.

When this happens your sim will get a notification that their friend has moved - if they had a relationship.

Housed sims that are not in 'My Household' can be culled once the games limit is reached.

But they still need to be manually added to My Households.

The Unlimited option for the Maximum Sim Count feature means you can add unlimited Sims to 'My Households', and make them protected.

The maximum number on the new culling system refers to the maximum number of sims you can place into 'My Households' and protect from culling.

Protecting sims/ghosts in 'My Households' also ensures these protected sims will not lose skills or relationships.

This creates a pool of sims that are 100% safe from culling and any skills or relationship losses.

Now households/sims can be placed into 'My Households'/favorited.Note: A higher limit on Sims could lead to an increase of load times, especially on slower machines. Go to: Options > Game Options > Gameplay and look for Maximum Sim Count and choose from 80 up to unlimited from the drop down list. The new total population cap is now 800 as of the Island Living Expansion. Culling will still happen but now you can choose which sims or ghosts will never be culled.

In a nut shell, the new culling system allows players to pick and protect their sims from culling.

No culling sims 4