Sorry I didn’t get back to you before… I didn’t get an email alert about your replies, and I just happened to check this page today.
I posted this because I believe I was once able to update the virus defs. manually in Avast Free, in the last few months, since I just installed it a few months ago… but then I couldn’t find that button again in all the settings.
I’m happy to know it’s updating so often behind the scenes. As for notifications every few minutes about the updates, I was used to a previous NOD32 paid antivirus app that momentarily flashed a tiny message box at the bottom left of my screen each time it auto-updated its virus defs. several times a day.