Suggestion add a index to wp_supporter table function, supporter_get_expire

I think this would be a improvement

Right now the is_supporter does not utilize a index in the datase.

Use something like
EXPLAIN SELECT COUNT( * ) FROM wp_supporters WHERE blog_ID = '27';

If you ad the following index
ADD INDEX blog_ID ( blog_ID , expire );

Then change the function to the below.
It will remove one query and the query will not actually have to open the table it could just use the pull the data from the index alone.
EXPLAIN SELECT expire FROM wp_supporters WHERE blog_ID = '27' ORDER BY expire DESC LIMIT 1

function supporter_get_expire($blog_ID = '') {
global $wpdb;

if ( empty( $blog_ID ) ) {
$blog_ID = $wpdb->blogid;
}

$expire = $wpdb->get_var("SELECT expire FROM " . $wpdb->base_prefix . "supporters WHERE blog_ID = '" . $blog_ID . " ORDER BY expire DESC LIMIT 1'");
if ( $expire > 0 ) {

return $expire;
} else {
return false;
}
}