Is it true that you should let the battery on your cell phone die before you charge it?

Question

Is it true that you should let the battery on your cell phone die before you charge it?
My friend and I were arguing about whether or not it is good to let your battery on your cell phone die before you charge it. I think that you should charge it everyday, but my friend says that that will kill the battery. They said that the rep at the cell company told him to let the battery die before each charge up and that will extend the life of the battery. That doesnt make sense to me but any input would be great. If someone has some supporting evidence or links for reference that is preferred. Thank you!

Answer

Its better to let it go as low as you can before you charge it. Obviously if I need the phone the next day I will recharge it before it drains but dont make a habit of recharging everynight or anything. It really will extend the life of the battery.