Let’s start with why longer-term results can be more predictable than shorter-term ones. The answer is, simply, averaging. One data point might be noisy, but as you accumulate more and average them, the outliers tend to offset each other. As a result, the signal starts to dominate the noise. The more data points you have, the closer you get to the expected result. Investors with 40 years, for example, can look at longer-term return goals with a reasonable expectation of actually getting them. But for shorter time frames, the noise can dominate. Hence, the extra caution needed as you get closer to retirement.