Excerpt: [F]inancial planner Ty Bernicke ... made waves earlier this year by suggesting that the ubiquitous online 'retirement calculators' actually overestimate how much Americans need to save. 'The reason they're inaccurate is that they don't account for the fact that as a person gets older, they spend less,' says Mr. Bernicke in Eau Claire, Wis. Even considering inflation, he says, 'an 85-year-old spends less than a 65-year-old.'