FM Transmitter for Honda Civic: Battery Drain??

I recently purchased Scosche FM Transmitter for iPod & MP3 which allows
me to use my non-Ipod MP3 player in my 2000 Honda Civic via the
cigarette lighter. In contrast to many other units, this one really
works well and has a very strong signal.

There are two potential drawbacks:
1. Only 4 channels (88.1, 88.3, 88.5, & 88.7); but two of the channels
work great for me, but it may not for others.

2. The more critical question is if I leave the unit in the cigarette
ligher, will it cause the car battery to drain? There is no on and off
switch for this device. And if it doesn't drain the car battery, would
keeping the device in the socket eventually cause corrosion of the
metal contacts? Should I unplug and replug the device each time I
start and leave the car?

I got this response from a technical rep from Schosche:

"Battery drain will depend on whether your cigarette lighter has
power constantly or only when the vehicle is on."

So, with 2000 Honda Civics, does the ligher have constant power or not?
I've read that some cars do and others don't.....

Thanks