An honest question!
Don't be bullied by pra**ts
If the master switch is left on then maybe some electrics will drain even if all instruments,radios etc are switched off.
There will probably be a small leak to earth somewhere,so maybe the battery will last between several days or possibly weeks,even months but it will definitely drain down.
On my race cars there is a master switch which is always off when not running,even so the batteries lose charge over a few months.
Lister
