Sitting in car with engine off

[spookybathtub]

I often sit in my car with the engine off, whether I'm listening to the radio, talking on the phone, etc. Is there any problem with doing this and leaving the key in the ON position for a long time? I have heard someone say that I should switch it to ACC in order to make some components last longer, but I don't quite understand that. I like ON simply because in ACC, there is an annoying beep when you open the door. And it's nice to have the clock display.

I'm installing a voltmeter so I can keep an eye on the battery.