My 2008 and 2010 Roadster were without voltage after 10 days. The 2014 4/4 holds its voltage for months.
The official workshop manual for my Fezza gives standard recharging intervals depending on battery drain whilst standing, The middle range is 60mA drain and standing for 15 days and this is with a car that by modern standards is pretty light on electronics but has a decent sized battery.
