When planning for retirement, most people immediately think about one critical question: "How much income will I need each year?" While that's important, it's not the full story. In fact, successful retirement planning relies on three key factors: Annual income needs (how much you'll withdraw from your portfolio each year) Length of time (how long you'll live) Growth of income (keeping pace with rising costs) Interestingly, many people heavily focus on the first factor and underestimate the...