All batteries will "draw down" and 12 volts are no worse than 6 volts in this regard {switching from 12 volts to 6 volts will not change a thing for the OP}. If the rig is going to sit for any length of time {and a few weeks should have little or no effect}, either provide some sort of battery maintenance like a small solar panel with a smart regulator or if AC power is available a trickle charge/maintainer.
The key here is to either eliminate all parasitic draws or simply disconnect the batteries. A decent {disconnected}, battery will still "draw down" to some degree while in a storage mode but not enough to do any significant harm unless it is ignored for many months.
:C