Limit maximum number of coupons/referrals user can earn

If for some reason you want to limit the number of coupons one user can earn via Refer a Friend plugin, add a code below to functions.php file, of course, change "20" to the number you want to limit to.

function gens_limit_number_of_coupons($raf_info,$order,$referrer_id) {
    $num_referrals = intval(get_user_meta($referrer_id, "gens_num_friends", true));
    if($num_referrals > 20) {
    	$raf_info = array("info" => "User has reached maximum number of referred customers.", "generate" => "false", "increase_referrals" => "false");
    }
    return $raf_info;
}
add_filter( 'gens_raf_order_info', 'gens_limit_number_of_coupons',10,3);

If you also want to hide the referral link after this, add the this code as well:

add_filter('wpgens_raf_link','gens_raf_link',10,3);
function gens_raf_link($raf_link, $referral_id, $type) {
	$user_id = get_current_user_id();
        $num_referrals = intval(get_user_meta($user_id, "gens_num_friends", true));
        if($num_referrals > 20) {
	  return "You have reached maximum number of customers you can refer.";
        }
    return $raf_link;
}