Don't allow users to checkout for the same level in PMPro if date is more than 3 months

disable_double_checkout.php

<?php

/*
	Don't allow early renewals for certain levels.
	
  (Don't allow users to checkout for the same level in PMPro if date is more than 3 months)
	Change the level IDs in the $pmpro_non_renewal_levels global array, then
	add this code to your active theme's functions.php or a custom plugins.
  
  Add the following code to your PMPro Customizations plugin -> http://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
*/

//define levels in global
global $pmpro_non_renewal_levels;
$pmpro_non_renewal_levels = array(1,2,3,4,5);	//change this to the level IDs of the levels you don't want users to renew for

//hide the renew link
function hide_renewal_links_for_some_levels($r, $level) {
	global $pmpro_non_renewal_levels;
	
	if(in_array($level->id, $pmpro_non_renewal_levels))
		$r = false;

	return $r;
}
add_action('pmpro_is_level_expiring_soon', 'hide_renewal_links_for_some_levels', 10, 2);

//redirect from checkout page to the membership account page
function redirect_non_renewing_levels() {
	global $pmpro_non_renewal_levels, $current_user;

	//make sure pmpro is active
	if(!function_exists('pmpro_hasMembershipLevel'))
		return;

    $enddate = $current_user->membership_level->enddate;

    $today = current_time('timestamp');
    $days_until_enddate = ceil(($enddate-$today)/3600/24);

	//if we're checking out, redirect to account page - change 180 to the number of days you would like users to checkout again.
    if($days_until_enddate >= 180){ 
        if(!is_admin() && !empty($_REQUEST['level']) && in_array($_REQUEST['level'], $pmpro_non_renewal_levels) && pmpro_hasMembershipLevel(intval($_REQUEST['level']))) {
        wp_redirect(add_query_arg('norenewal', '1', pmpro_url('account')));
        exit;
    }
    }
	
}
add_action('template_redirect', 'redirect_non_renewing_levels');

//show message on the account page
function the_content_add_non_renewal_message($content) {
	global $pmpro_pages;
	if(!empty($pmpro_pages) && is_page($pmpro_pages['account']) && !empty($_REQUEST['norenewal']))
		$content = "<p><strong>You must wait before renewing your membership.</strong></p>" . $content;

	return $content;
}
add_filter('the_content', 'the_content_add_non_renewal_message');