How long can my sims live at most before he or she dies?

Aging settings can be accessed through Gameplay Settings.

For this, open the menu (three dots in the upper right screen) and choose Options. In the right, choose Gameplay. And in there, you can change the aging settings: set the length and even turn on or off aging (for played or unplayed households separately. It is also possible to have only the active household age).

This setting is different in each save. So you need to have loaded a save in order to change those settings.