Over the many years that i have owned cell phones since they started with the lithium ion batteries i have never drained it till the phone died. And i have never fully charged the phone when i 1st bought it before using it cause its a new toy, I want to use it right away. I will put it on the charger that night when i go to bed. I do this every night and just unplug it in the morning when i get up. I easily have enough battery juice to last me all day long. Somedays i use 30% battery and somedays i use alot more. I have never had an issue by charging my phone in this method. Battery University states that charging a lithium ion battery more frequently the battery preforms better than letting it discharge till its very low and then charging it is harder on the battery. The Battery in your iphone should have about 400 to 500 charge cylcles, meaning 1 charge cycle is charging 100%, so if you recharge your battery when its at 50% one night and then recharge it when it is at 50% again the next night, this counts as 1 charge cycle. Many people think that every time they plug in and recharge their iphone battery that is 1 charge cycle, that is false.
Many people have their own myths, beliefs, or what ever you call it on how to take care of your battery. I will never change my way no matter what others say because i have a proven track record of over 10 years of using lithium ion batteries and know what works for me. Just thought i would share my info with you. You can use it or just disregard it. Your choice.