Lot Challenges/Lot Traits - How do you use yours?

I personally assign per lot according to the family who lives there, not per world.

Because to me, not every single house is effected by the same thing.

Like if a sim living in a house is a slob, then I would add the Filthy trait to lot.

I would not assign that same trait to say the Landgraabs because obviously they are wealthy enough and would have hired help to keep the house in pristine condition.