I used to undo the negative cable if the car was going to sit for any length of time. When I got tired of disconnecting the battery to keep it from dying, I finally installed a battery cut off switch. It is much easier to turn off the battery, now, and the battery lasts a lot longer. I have a digital clock in the radio, which is a slow drain. I never tried to see if there is any other parasitic losses.
I made a bracket and mouted it to the inside of the right fender, behind the battery, just below the hood line. I need to redo it because the hood lightly touches the bracket. I don't have any pictures, but will see about putting some up another time.