<p>This paper addresses limitations of fixed timing and rigid plans in traditional age replacement policies, focusing on interval replacement with minimal repair for parallel systems of independent identical components. A general framework for the policy and associated optimization with <i>n</i> as a key parameter is systematically presented and analyzed. The proposed interval-based preventive maintenance model assumes scheduling maintenance within a time interval is more practical than fixed-point maintenance. Compared to traditional strategies, it introduces greater flexibility in policy development; while cost rate functions differ marginally, the new model enhances implementation effectiveness, efficiency, and convenience. Notably, these findings extend existing literature by shifting focus from age-centered to interval-driven replacement. They also demonstrate strong adaptability in benchmarking against constant-component systems, aligning with reliability engineering validation practices through consistent cross-configuration performance.</p>