An advice? Unless you need the ghosts, don't kill the sims - but pretend to do it. Then you can re-use the sims later

I've got a bunch of sims that I re-use all the time for stories or as contest extras. Half of Pleasantville is full of them, actually... Only by changing clothes and/or hairstyles, I'll have entirely "new" sims which actually does look like new sims.
I even have some "stunt sims" (if I can call them that), and "doubles" for the main characters. For some of them, I even have all ages from Toddler to adult, in case I need some "backflash" photos. Even some extra babies

Another tip - if you have Seasons, then you can put 8 different hairstyles on the extras - which gives you eight sims in one

Perfect if you've got a slow computer or need several sims you can use several times.