Some newer vehicles get upset when you do that, but older ones generally don't. You may lose radio programming though. I've got an old '95 Caravan that's going to be getting a quick disconnect like this one pretty soon though; the drain takes a few weeks to kill the battery, but we don't drive it very often either. Why do we still own it? With the back seats removed, you can easily put 8'x4' sheets of plywood in it.