If you use a laptop, and your battery dies quickly, check and see if you accidentally left iTunes open on an iTunes Store page, even in the background. Look how much CPU it uses to simply display a front page, and rotate graphics in the carrousel at the top of the page (the display is from iStat Menus):
Lest you think that a lot of the CPU that iTunes is using is to play that Allman Brothers song, here’s what happens if I switch out of the iTunes Store.
Together, iTunes and coreaudiod, which processes audio played by iTunes or other apps, use about 7% of CPU.
So don’t leave iTunes open on an iTunes Store page in the background if you’re using a laptop.