Co incidentally mine and thedunn805 views are same. Charge it completely till you get plug sign on phone. Use the phone till battery reaches below levels of 4%. As for the people who charge their phones daily or when battery is below 20% will have to deal with a phenomenon called memory effect. We are reducing the usable capacity of the battery by recharging it on a daily basis.
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Problem with this method is that it isn't alway possible and most people just don't know or do that. I charge my phone like I usually have. Put it on the charger when I go to bed and take it off when I wake up. I have never had it die during my time awake. Closest I actually got was yesterday I was at 3 percent when I went to sleep and charged it. I don't know many people who are going to sit by their phones and wait for them to be fully charged. If your working at a desk maybe, but I don't know anyone who waits till a phone dies and takes it off as soon as its charged. I remember old phones you had to do this, however newer batteries are made to stop charging as soon as the phone is full. Even if you charge every night your battery should be ok until you trade in your phone. Battery life daily varies based on apps used, services used and apps in the background (in ios location based apps can kill your battery if on in background and in a low service area)
Now please don't get me wrong, I believe your methods may work! However, even if charging overnight everyday was really bad, most people need their phones during the day. Why let it die during the day time and then if I am out and need it be screwed? Smartphones are awesome little computers but they still are and always will be a mobile communications device which loses its point if It dies while out of the house and its dead when needed. Believe me.... My last three smartphones never lasted a day and I ALWAYS needed them when they died. I had to turn off radios, turn off the phone when I didn't need it, not use it for anything other than texts. I had webos, windows phone and android, and did it for all three. Android and webos were the worst offenders and it was around the beginning of their lives this problem happened so I am sure it was not from battery degrading, it was the way the systems ran. On my iphone I get between 13 hours with 6 used and more than 20 with 4 used. I have forgotten to charge it before and it lasted a day and a half so I really am not too worried.
I look forward to a day when we don't have to worry about battery life at all though