Also what is the automatic update interval default setting, can it be altered?
At the top right of the main display, look for the "Settings" button.
Click on it.
Click on "Updates".
Click on "Details" in right pane.
Change Auto-update interval.
The default is 240 minutes. Note that if you change the value, it probably
won't take effect until after avast! has been restarted on the next boot.
That's been my experience.