http://forums.mozillazine.org/viewtopic.php?f=37&t=2979947Well, I tracked down what's causing the ETL file to update every day. It's coming from a task in Task Scheduler called Microsoft Compatibility Appraiser which belongs to the Customer Experience Improvement Program except that I opted out of that when I first bought the laptop in February last year.
So it would seem that M$ has just chosen to ignore users wishes and send telemetry data every day regardless.