After working with people on retirement planning for years, I’ve noticed that the mistakes people make rarely come from ignorance. Most people know they should save. They understand inflation exists. They’ve heard about healthcare costs. The problems emerge elsewhere – in the gap between what someone plans on paper and what actually unfolds when they stop working.
The most common error I see is underestimating how long retirement will last. People calculate based on life expectancy tables, which give an average. But average is misleading. If you’re healthy, married, and come from a family with longevity, the odds shift significantly. A 65-year-old couple has roughly a 50% chance that at least one of them will live into their mid-90s. That’s not a worst-case scenario – that’s the actual median outcome. Yet I regularly see retirement plans built on a 20-year horizon when the real planning window might be 30 or 35 years.
This matters because it compounds. A plan that works for 25 years can collapse in year 28 when the math simply runs out. People often discover this too late to adjust meaningfully. By then, they’ve already retired, stopped earning, and lost the most powerful tool they had: time to recover from shortfalls.
The Spending Assumption Problem
Another pattern I’ve observed repeatedly involves spending estimates. People typically project that they’ll spend less in retirement than they did while working. This makes intuitive sense – no commute, no work clothes, the mortgage might be paid off. But the actual data tells a different story for many retirees.
What happens is that people replace work-related expenses with leisure and travel. They have time to do things they couldn’t before. Healthcare costs, which are often underestimated, rise faster than general inflation. Home maintenance that was deferred during working years suddenly becomes urgent. A roof that needed replacing five years ago doesn’t wait for retirement to fail.
The deeper issue is that spending in retirement isn’t constant. The early years, when people are most mobile and healthy, tend to be expensive. Travel, new hobbies, visiting family – these things cost money. The spending pattern is often front-loaded, not evenly distributed across 30 years. Yet most plans assume flat or gradually declining spending. When reality doesn’t match the model, people either cut back sharply (which defeats the purpose of retirement) or they deplete savings faster than planned.
Inflation and Healthcare
Healthcare inflation deserves its own attention because it behaves differently from general inflation. Over the past two decades, healthcare costs have consistently outpaced overall inflation. A plan that assumes 3% annual inflation might work fine for groceries and utilities but falls apart for medical expenses. Long-term care, in particular, is a blind spot for many people. The cost of assisted living or in-home care can easily exceed $60,000 to $100,000 annually in many regions, and those costs rise year after year.
I’ve seen people with otherwise solid retirement plans get derailed by a spouse requiring extended care. They didn’t ignore the possibility – they just underestimated the duration and cost. Medicare doesn’t cover long-term care. Medicaid does, but only after you’ve spent down your assets to qualifying levels. The gap between what Medicare covers and what care actually costs is where many retirements get tested.
Sequence of Returns Risk
There’s also a mathematical reality that doesn’t get enough attention: the order in which investment returns happen matters enormously in retirement. If you retire just before a major market downturn, you’re forced to withdraw money from a declining portfolio. That’s different from experiencing the same downturn five years into retirement, when you’ve already built a cash buffer and haven’t needed to sell assets at depressed prices.
I’ve watched retirees who were financially secure on paper become anxious and make poor decisions because they hit a bear market in their first few years of retirement. They see their portfolio drop 30%, they’re withdrawing for living expenses, and the math suddenly feels fragile. Some cut spending unnecessarily. Others shift to overly conservative investments, locking in losses. The sequence of returns doesn’t change the long-term average, but it absolutely changes whether a specific retirement plan survives.
Social Security Timing
Social Security claiming age is another area where I see recurring miscalculation. People often claim at 62 because they can, or because they think the system won’t be around later. But the math of delaying is powerful, especially for people in good health or with family longevity. Delaying from 62 to 70 increases your monthly benefit by roughly 75%. That’s not a small difference over a 25-year retirement.
The mistake isn’t always claiming too early – sometimes early claiming is the right choice. The mistake is claiming without doing the math. I’ve seen people claim at 62 and then spend the next decade wishing they’d waited, watching their monthly benefit stay fixed while their portfolio gets depleted faster. Conversely, I’ve seen people delay claiming while drawing down investments at high rates, paying taxes on that withdrawal, when they could have taken Social Security and preserved their portfolio.
The claiming decision interacts with everything else in the plan. It affects taxes, it affects portfolio drawdown rates, it affects spousal benefits if applicable. Yet many people treat it as a standalone decision rather than part of an integrated strategy.
The Flexibility Gap
One thing that separates plans that survive reality from those that don’t is built-in flexibility. A plan that requires everything to go exactly as projected is brittle. Markets will fluctuate. Spending will vary. Health will surprise you. A more resilient plan includes decision rules: if the market drops this much, we adjust spending that way. If we live longer than expected, we make these changes.
The people I’ve seen weather retirement challenges most successfully are those who planned with multiple scenarios and built in adjustment mechanisms. They weren’t trying to predict the future perfectly. They were building a system that could adapt when the future didn’t match the forecast.
Most mistakes in retirement planning aren’t about missing a single factor. They’re about underestimating how variables interact, how long retirement actually lasts, and how much flexibility you’ll need when assumptions meet reality. The plans that hold up are those built with margin for error, not those built on best-case scenarios.
