And that takes us to the second question of how much can I spend. It really matters how long you live. Here's a funny thing. If asked, many people have a different answer depending on how the question is posed. You might answer differently if asked whether you will live to a certain age, versus if you were asked whether you will die by a certain age. That's because we often think of different things when each question is presented. When asked whether we will live to a certain age, we tend to think of the reasons we will live that long. When asked whether we will die by a certain age, we tend to think of the reasons we will die.
If you were asked how long you expect to live, what would you answer? While it might make sense to be very conservative, after all most people are afraid of running out of money, it also means that we could be imposing a restriction on our life unnecessarily. I ask people whether they'd like to take a longevity test. It may not be prescient, but I think it beats simply guessing.