How often should I ping my site?

Sorry but you're wrong. I don't understand why people reply to blog posts and advise if they are not 100% sure what they're talking about. No disrespect but it only misleads people with the wrong advice.

There is absolutely no penalty for over-pinging. You will never get deleted from Google or penalised in any way because if that was the case then my competitiors would try to knock me off top spot for my chosen keyword. Google can't penalise in case compitiors are malicious with over-pinging and other malicious behaviour. However, if you do over ping then Google just ignores your website for a while. It's still indexed and un-penalised but by over-pinging you will b wasting your time. I hope that helps you more.