It would be nice if avast! would be displaying a warning (just like for disabled shields) inside status page when Self-Defense is disabled and offer a "FIX" button for it.
Sometimes users might be fiddling with this setting and forget to enable it back.
These days Self-Defense is a critical part of antivirus and as such it would be a smart thing to notify user about it when Self-Defense is disabled.
Like we say it, better safe than sorry right?