Interesting question...

I flew a trip with a guy who said: I am quitting as soon as my trades replace my income.

My response: I would never retire if I had to count on my trades.

The point is, money is just a tool. It is not security or happiness or longevity. When you have "enough" money, you realize how little the world has to offer materially. In this life, you have to do something to fill up your days. I like flying paid mini-vacations to go to places most people can only dream about going.