I've added many new cats to my family over the years, but they've generally been the type to just fall into your life rather than the planned kitty variety, so the how and when has never been something we could really plan.
If one is planning to get multiple cats (probably mostly adults) all from different litters and that have never been socialized together before, does it make more sense to add the new cats to the household one at a time to minimize the amount of change happening all at once, or does it make more sense to get all the cats at once, so that the living situation isn't constantly changing, and after the initial shock, everyone can get comfortable with the way things are? Keep in mind, this would be adding to a household that already has two cats, so there's already territories and a hierarchy established within the house.
