What happens if I have more than 400 active sims in "my households"?

Basically I want to keep both my original households and the townie households in "my households" instead of "other households". I do this because otherwise, the townies autonomously die or get married and move between households. I've tried using mods and the settings to stop that, but they still do it. I

'm wondering how much it'll hurt my laptop if I do that, though.