The central risk of retirement is not dying poor — it is living longer than you planned for, which is a form of good fortune that the financial system tends to punish. Managing a finite pool of assets across an uncertain time horizon requires a different orientation than accumulation: spending rates, sequence of returns, and healthcare costs become the dominant variables. Reason says the plan you build at 65 should account for a person who lives to 90, because many do.
Each step builds on the last.