Strange electrical fault again

[green A8]

I'm not sure if I've raised this fault on this forum before I think I might have.

The car is a 2000 MY FL 4.2 QS with only just over 20K miles from new It's owner works abroad so the car is laid up for three to four months at a time. A couple of years ago the car was being readied for return to use The garage had removed the battery which was to be replaced with a new one. On connecting the new battery and starting the car the battery light glowed brightly and the new battery was quickly discharged. A new alternator was fitted the battery recharged and all was well. Fast forward two years and only three thousand miles and exactly the same thing has happened again. Is it normal for alternators to die through lack of use and at such low mileage? any ideas as to the underlying cause? No faults of any sort were found via VCDS.