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Sleep researchers have increasingly challenged the notion that a single ideal amount of sleep applies uniformly across a population. While eight hours is often cited as a general benchmark, longitudinal studies tracking individuals over years suggest that consistency of sleep timing may matter as much as total duration for measures of daytime alertness and metabolic health. Subjects who slept seven hours nightly at a fixed schedule sometimes showed better cognitive performance than those sleeping eight hours at irregular times. Researchers caution, however, that these findings do not license indefinite sleep restriction; rather, they suggest that public health messaging focused solely on a duration target may overlook a second, independently important variable: regularity.