The inverter will run the battery down after about 3 days to a week, depending on the size of your battery and or inverter.
My battery is a cheapy, and runs down after leaving the door open without the key in (How it beeps) after about 30 minutes.
Clarion 200watt head unit w/ Aux in.
Kicker 800watt 4 channel amp
In a 96 Grand Prix SE.