Yes, I understand that, but what is the failure mode - is it gradual or rapid? If it is rapid, then the system keeps shining even when it appears almost empty.

Yes, I understand that, but what is the failure mode - is it gradual or rapid? If it is rapid, then the system keeps shining even when it appears almost empty. If gradual, then I probably need to revisit what I learned of quasars done decades ago...