If an update fails, the panel say so.
It's a pity that you cannot control the panel to be "always shown until manual dismiss".
Sort of disagree,
Because people would say,
"What's that message doing there and why do I have to keep manually clicking on it to close it?!" Several people who would not like such a change.
However, there is good news in an answer for this question! In Avast 5, if you wonder about the status of an update, just right-click on the Avast Ball in your System Tray (next to the clock) and select, "Show Last Pop Up Message." That will tell you Avast's last action. You can pin the message up, selecting the little push pin in the message. When you want to close it, or just "x" out of the message. (click the "x" manually when you have read what it says.)
This feature is very helpful if Avast found or blocked a threat, and you want to read what it says about it for further study.
Jack