Question about the ECU?

[94svxred]

My car sits in the garage , sometimes for a week maybe two before i start it or drive it . So here is the question ,If the battery gose dead and can't start the car! To what point will the ECU reset or in my case there is still a little bit of juice but not enough to start the car?( basicly a dead battery) Is the ECU still working or will it reset? Is this bad on the ECU or should I disconnect the battery when my car sits?