Walking is essential for maintaining independence and quality of life, yet aging may impair the neuromuscular function required for stable gait over time. This study sought to quantify age-related differences in step-to-step control during prolonged walking using detrended fluctuation analysis (DFA). We hypothesized that step-to-step changes in step length and step width would exhibit reduced temporal persistence over time, with more pronounced effects in older than in younger adults. 15 younger and 15 older adults walked on a treadmill at their preferred speed for 30 min. Kinematic data were used to calculate step length and step width across six consecutive 5-minute bins, from which DFA scaling exponents (α) were computed to characterize the temporal persistence of foot placement control. Younger adults exhibited clear adaptations over time, including the adoption of longer and narrower steps with reduced step width temporal persistence. In contrast, older adults showed relatively invariant step kinematics and DFA α-values over time. Younger adults may adjust their foot placement strategy over time to minimize energy cost and/or to accommodate fatigue. Conversely, our findings highlight a reduced capacity to adjust foot placement in older adults during prolonged walking, which may arise from diminished sensory feedback and may contribute to an increased risk of instability and falls. By revealing how the temporal structure of gait changes with age during prolonged walking, this work offers insight into the factors contributing to mobility decline and may inform interventions to support adaptive gait control.