If you know exactly when you'll die and the sequence of future expenses you'll incur between now and then. Having money is useful insurance. It's all about ask

If you know exactly when you'll die and the sequence of future expenses you'll incur between now and then. Having money is useful insurance. It's all about asking the marginal benefit of saving or spending each additional dollar. At some points, you derive more out of spending -- such as when you're spending them on basic necessities, or when you have a large pile that can already cover those 99th percentile emergencies. And, of course, being able to estimate your own utility for those. Which is hard.