I wouldn't call this very effective. It would take an impractically long amount of time to capture a meaningful fraction of the collection and quality would suffer greatly.
Even if you plug the audio output into the input you would still be taking a quality loss by passing the audio through a DAC and then an ADC. Maybe if the quality of your hardware is good enough it wouldn't matter, but then you would be limited to only ripping 24 hours of audio per day...
