Unlike most other video games, if your Sim dies, you can't just get another life and start over again at the beginning of the level. But there are a lot of ways around this, depending on what kind of life extension you're looking for. 

 

When choosing a life extension method, ask yourself whether you want to  have more time at each life stage, to be whooshed back to Young Adult, or to have more days tacked onto your given lifespan.

 

The default lifespan is "Normal," about 90 days. But you can change this setting in the Options menu to "Long" (190 days) or "Epic" (960 days). 

Each time you eat a Life Fruit, it adds one day to your lifespan (i.e. you continue to age, but you live longer). Theoretically if you ate enough of them, you would never die. Somehow this reminds me of a Looney Tunes cartoon character: as long as you lay down the board for your bridge faster than you run, you can get across that canyon!

 

Both joggers and vegetarians live longer. In the case of jogging, you have to run at least 500km in order to get the lifespan boost.

 

Vampires and mummies live about twice as long as normal Sims,  

 

Getting to the point where you can make Ambrosia is a challenge in and of itself! Get a Death Fish, a Life Fruit, and enough Cooking skill to learn the recipe for Ambrosia and your age will be reset to the beginning of your life stage. 

 

The Generations expansion pack brought us the Young Again potion. Drink it, and your age will be reset to Young Adult day 1. You can either learn to make the potion with the chemistry set, or buy it as a Lifetime Happiness Reward for 70,000 Lifetime Happiness points.

 

Also introduced with Generations, this Lifetime Reward freezes your age as it is at that moment. Costs 65,000 Lifetime Happiness points.

 

The Hidden Springs mini-expansion included a new Décor item available in Buy Mode: the Fountain of Youth, for $495,000. You have two interactions: "Drink," which adds a day to your lifespan (like Life Fruit), or "Wish For Youth." 

 

If your wish is successful, you will be reset to the beginning of your lifespan. If your wish is unsuccessful, you will stay the same age, and one of your existing traits will be replaced with the Childish trait.