The 4% rule and most retirement calculators often just assume you are going to spend the same inflation-adjusted amount of money for the next 30 years. On the one hand, this is a simple and clean idea for managing finances, but it's also completely wrong. Real retirement spending rarely works like it's supposed to, and if you are planning on it being static, you're likely setting yourself up for a big surprise.
A 65-year-old man today can expect to live to 84 years old, while a 65-year-old woman can expect to live until 86. For plan sponsors and advisers, that translates into a potential distribution horizon of at least 20 to 30 years. Without incorporating realistic longevity assumptions into glide path design, withdrawal strategies and income solutions, participants face a heightened risk of outliving their savings.