When you use Google Notifier you will have noticed that your mailbox will be checked once every 15 minutes. You can change this interval with the following Terminal command.
First, close the Google Notifier application. Click menubar icon and select ‘Close all Google Notifiers’
defaults write com.google.GmailNotifier AutocheckInterval x
Where ‘x’ is the number of minutes between checks.
Restore to default 15 minutes setting with:
defaults write com.google.GmailNotifier AutocheckInterval 15
You can do the same thing by clicking on the icon, then holding down Alt and Command when you click on Preferences. Enter the key AutocheckInterval in the desired value.