I have an IBM Thinkpad 600E, an ancient workhorse of a model, quite
reliable. I get about 2:15 of battery life out of it under normal
circumstances, and the battery's almost a year old already.

Now, the one thing that I have noticed is that if I listen to music
(MP3s, specifically), my battery lifespan drops to about 1:30. Is this
normal? It can't be the CPU; I typically run it pretty hot, and the
battery life doesn't seem to be affected by doing full-screen video,
just audio. If I turn the soundcard off and run a movie, I still get
more than two hours.

Is this expected? Can one piece of hardware really suck up so much
power, even if I'm using headphones?