once a day. there is no need to do it regularly. if you ask this question, it means that you can't wait to get that money and may click on your own ads. be careful.
Only once when I wake up in the morning. When I'm new with Adsense, I checked my account almost every hour. - Dynashox -
I only do it every end of the day. Since I rather use the time for refreshing to promoting my website more especially to my friends in Facebook. Every minute counts when you have the power to promote your site for more traffic.