In the United States, the majority of the population is not regularly physically active in accordance with established national guidelines. Research has uncovered several variables that show significant and consistent relations with physical activity, including some that refer primarily to cognitions (e.g., appraisals of personal capabilities, such as self-efficacy, or beliefs about health benefits, such as cognitive attitude) and some that refer primarily to affect (e.g., beliefs about deriving pleasure, such as affective attitude, and experiences of enjoyment). It has been suggested that cognitive variables might be more strongly associated with physical activity during the early stages of participation, but affective variables might be more strongly associated with physical activity during later stages. The present study aimed to empirically test this suggestion. Therefore, the hypothesis was that length of time (in weeks) of being consistently physically active would moderate the relation of cognitive correlates (self-efficacy, cognitive attitude) and affective correlates (affective attitude, enjoyment) with the current level of physical activity. Using the Amazon Mechanical Turk platform, 747 US-based adults completed questionnaires that measured: (a) current physical activity, (b) cognitive attitude, (c) exercise self-efficacy, (d) affective attitude, (e) physical activity enjoyment, and (f) physical activity history. The results confirmed that all postulated correlates (cognitive attitude, exercise self-efficacy, affective attitude, physical activity enjoyment) exhibited significant (all p < 0.001) and meaningful relations with current physical activity. Furthermore, a positive relationship was found between current physical activity and physical activity history in weeks (r = 0.303, p < 0.001). However, physical activity history was not found to significantly moderate the relation of any of the postulated correlates with current physical activity (R2 change for the addition of the interaction term < 0.06%). This finding suggests that the strength of the relation of cognitive and affective variables with physical activity does not change in a systematic way as a function of the duration of continuous participation in physical activity. In turn, this finding implies that efforts to promote physical activity participation and adherence should maintain a balanced focus on cognitive and affective factors. Methodological strengths and limitations of the study that may inform future investigations on this topic are also discussed.