@owlgetyouThere are separate settings in your Game Options under the Gameplay tab for Auto Age (Played Sims) and Auto Age (Unplayed Sims). If you choose to allow Auto Age for Unplayed Sims then you can choose from three different Sim Lifespans-- short, normal, or long.
This is how I have my game set up. I disable aging for all Sims, both played and unplayed. Whenever I decide to age any of them up I'll just do it manually in CAS (through the Manage Households screen) or I will use a birthday cake. Many other players choose to do it otherwise and let all or just some of the Sims age automatically. It all depends on how you want to play your game.
