I take a look at every premade family whenever there's a new pack, even though I rarely use them, and while I can't remember everyone's name and face and history, I usually remember something about them when I see them in the game. That being said, I find the Eco Lifestyle premades rather forgettable. I remember the woman who keeps calling to make you donate 1$ (just don't ask me what her name was), but that family where the teenage son wears a bag over his head, I probably wouldn't even recognise them if my sims ran into them in public.
Oh, and there was that one time I killed a premade by accident. Well, no, the killing wasn't an accident per se, but I assumed he was a randomly generated townie because of his awful clothes, and my occults don't mind using those for target practice. The premades are usually left alone as long as I don't need them, except for... well, that one case.