The longest I can keep a battery alive is about 18 to 20 months. Despite using Bosch S4 008 battery with 680A 74Ah capacity. Leave the car for 4 days, flat!! The car just destroys them.
The AA are not happy replacing them under their 5 year warranty, they have checked charging system and parasitic draw, which were all fine.
Do these cars just destroy batteries FOR THE SAKE OF IT?
These are heavy on batteries, as was my Citroen XM.
I often approach my car and hear the electric mirror motor whirring despite the car being locked and unattended for several hours. It’s French - designed to charm and irritate in equal measure,
Trev it seems some of the Vel Satis suffer from this battery drain issue. All i can suggest is that you pay a good auto electrician to do some tests as to where the voltage is being drawn. I know of some cars that have had extras wired in having drain faults, such as ones with towbars or carphones but sometimes it can even be a faulty alternator that is drawing small load from the battery when it is not meant to.