It appears to me that when you set the display to avergae 5 seconds, etc....it still updates the display every second or so, but it is showing numbers that were averaged over the sample rate you picked.
In other words let me draw a picture of 5 second averaging:
Sample:1--2--3--4--5--6--7--8--9--0--11--12--13--14--15--16
Display:------------1-5--2-6--3-7--