function post_published_limit() {
$max_posts = 3; // change this or set it as an option that you can retrieve.
$author = $post->post_author; // Post author ID.

$count = count_user_posts( $author, \'CUSTOMPOSTTYPE\'); // get author post count


if ( $count > $max_posts ) {
    // count too high, let\'s set it to draft.

    $post = array(
    \'post_status\'   => \'draft\'
);

    wp_update_post( $post );
}

希望这是你的答案。