The amount of Bright Eyes I listen to is just ridiculous, I don't even have all of their cd's yet and my play count is unbelievable. Particularly Lifted or The Story is in the Soil Keep Your Ear to the Ground.
Hmmm...good question. There are bands I will go months or weeks without listening to, but they find their way back in my CD player in my car and my mp3 player (Godsmack, Seether, Disturbed, Evanescence, 12 Stones, Chevelle, Avenged Sevenfold, Lacuna Coil, etc). These days the bands I cannot go without are Epica, Within Temptation, Kamelot, Nightwish (and Tarja), Mediaeval Baebes and Pyrates Royale (see my page for songs). All my CDs at all times stay in my car, because I never know what I'll be in the mood for, especially for long trips between school and home.