function edd_sl_check_for_expired_licenses() {

    $args = array(
        'number'     => -1,
        'parent'     => 0, // Child keys get expired during set_license_status()
        'expiration' => array(
            'start' => strtotime( '-1 Month' ),
            'end'   => current_time( 'timestamp' ),
        ),
        'status' => array( 'active', 'inactive', 'disabled' ),
    );

    $args      = apply_filters( 'edd_sl_expired_licenses_args', $args );
    $licenses  = edd_software_licensing()->licenses_db->get_licenses( $args );

    if( ! $licenses ) {
        return; // no expiring keys found
    }

    foreach( $licenses as $license ) {
        $license->status = 'expired';
    }
}
add_action( 'edd_daily_scheduled_events', 'edd_sl_check_for_expired_licenses' );