Make any post older than 7 days, form a specific category available for free with Paid Memberships Pro.

make_old_posts_free.php

<?

/*
	Make any post older than 7 Days available for free.

*/
function make_old_posts_free($hasaccess, $post, $user, $post_membership_levels)
{
	//if they already have access, let them at it
	if($hasaccess)
		return $hasaccess;
// Categories that this code should apply to. Categories not here will assume default functionality.
    $categories = array( 'catone', 'cattwo' );

    if ( ! in_category( $categories, $thepost ) ) {
        return $hasaccess;
    }
		
	//only make posts of type post (i.e. not pages or other CPTs) free
	if($post->post_type != 'post')
		return $hasaccess;
		
	//now check the publish date
	$published = strtotime($post->post_date, current_time('timestamp'));
	if($published < strtotime("-7 Days", current_time('timestamp')))
		$hasaccess = true;

	return $hasaccess;
}
add_filter('pmpro_has_membership_access_filter', 'make_old_posts_free', 10, 4);