Testing has shown that the MDS manager has a very small battery draw when the vehicle is off and in "sleep" mode. This is because it needs a monitor running to catch when the vehicle is started. This small draw is not enough to adversely affect battery life or drain the battery unless left in place for an extended period of time (i.e. more than a week).
Our testing has shown that in the normal vehicle, it shouldn't affect vehicle starting for several weeks HOWEVER very cold weather can drastically reduce battery capacity, as well as any other accessories or modules in the vehicle that stay "awake" with the key off. Many security systems, aftermarket radios, plug in phone chargers and so on may have a slight drain when not in use, so best practice is to unplug the MDS Manager when you know the vehicle is going to be sitting without starting or driving for several days.