As one who keeps my systems up to date with all the Avast releases, I have personally seen it mess up exactly once in nearly a decade of use. I came here, got advice to do a full removal and reinstall, and I was back up and running.
That shouldn't have been necessary, but anyone can be forgiven for making a mistake. From my perspective the Avast team appears to work very hard not to make them.
Being conservative seems reasonable but you have to balance risk and benefit.
The very source of goodness in a web-integrated anti-malware product is in its ability to bring you the wisdom of the latest detection logic. Blocking its update for a significant length of time opens you up to new malware, and the designers know that, hence the alternate "emergency update" facilities.
If you're relying on your anti-malware software as your main line of defense (which you shouldn't be), allowing it to grow out of date is akin to just running without it. You're not browsing old sites with old ads. Malware writers are constantly busy.
If you're unsure about your options, take the time to go through all the panels and review their settings. You seem to want to be fully in control, and this is the only way to know it's set exactly the way you want it.
-Noel
