A premium account allows you to store a number of URLs (depending on the package you sign up to) in your account.
These URLs will be automatically pinged every three days or more depending on the package that you are subscribed to. As a premium member you should not need to ping your URLs manually, that feature is for the free ping service.
The URLs that you add to your Pingler account will be pinged automatically after you add them into your account. You are entitled to whatever number of URLs according to the package that you are subscribed to.
If you keep the URLs in your account, they will continue to be pinged automatically.