expiration of contents with meta_post

hi
i writing this code for expire post:

add_action( 'expired_post_delete', 'delete_expired_posts' );
function delete_expired_posts() {
	$todays_date = time();

	$the_query = new WP_Query('post_type=post');
	while ( $the_query->have_posts() ) : $the_query->the_post();

		$getmyvar = get_post_meta( get_the_ID(), 'getdateexpire', true );
		if(!empty($getmyvar)){

			if ( $getmyvar < $todays_date) {
					$my_post = array(
						'ID' => get_the_ID(),
						'post_status' => 'pending',
					);
					wp_update_post( $my_post );
			}

		}

	endwhile;
	wp_reset_postdata();

}

now problem is when i add this in function.php , site was slow loaded.
and another problem is , add_action() It does not work and must add this delete_expired_posts();
What is the problem?