Character Cull Distance?

Hey guys, so im sure this have been asked befour but i cannot find an answer.

If you make a big open world with lots of characters and stuff, how should you deal with the distance?

I mean the boxvolume that removed object after a surtain distance based on size doesnt affect Actors right.
Should i just let all the actors be render all the time? sounds like a waste of memory since all the polygons on them will consume alot after a while.

And i dont wanna Destroy them after a surtain distance since maby the characters carry a variable of some sort.

Is it possible to just make them invisible at a distance so they arent rendered. But they are still there. or would that still require alot of memory?

I know the game “Oblivion” have what they call radiant AI, their always active and making their tasks even if the player are miles away.

Thanks in advance! :smiley:

I also want to know this “secret”…