I use Kenwood in my 91' CRX. I have it wired directly to the battery (that's how the wiring was setup when I installed it...so I just left it. I will be wiring it through the fuse box sometime soon!!!)...and even though it's technically "on" all of the time (it just flashes a little red light, and if the head unit is in, it'll put a graphic on the CD player..animated). Even though it's like that, it's fine overnight, for a good 8 hours when I'm at work, etc. As far as listening to it without the car running, I've done it not quite an hour, but pretty close to that..no probs yet!