How Many Households?

I focus on just one, which is why I voted that way, but if I have my main household "settled" and can let them go on autopilot for a sim week or two (everyone's achieved the job level I want, the kids have their aspirations settled, the toddler's maxed out) I'll sometimes pop around to another household to set things up for the next story I want to tell. Especially if it involves getting what are intended to be NPC's to certain levels without cheats because said cheats are buggy. (University, Realm of Magic)