You can also purchase Heirlooms in the store.
These Heirlooms can be used to earn new traits, career levels, and hobbies. When your Sims retire, they will leave behind an Heirloom for your other Sims. Sims can retire once you reach level 16 and they have maxed out their traits, but only if you want them to. At the end of the elder stage, Sims will die of old age. On the normal lifespan setting, elders will always live to be at least 90 days old, resulting in the elder stage lasting for a minimum of 16 days before death becomes a possibility.