Billing and distributed pollers

Hi all

I have a distributed poller setup with RC poller. I need to run billing on ~1000 devices. My question is, what should the configs look like? At the moment I have $config['enable_billing'] = 1; on my web server (which does only apache and rrdcached) and on all the pollers

$config['service_billing_frequency']           = 300;    # Seconds between billing calculations
$config['service_billing_calculate_frequency'] = 60;     # Billing interval

My question is, is this correct, or should the calculation of the billing be done on a single machine i.e. in my case the web server? To lessen the load on the pollers?

Regards
Hans