Difference in battery life - wall vs computer

[Hawk]

There is your problem. You should not let you battery drain down that low every time. Li-ion batteriies only have a certain number of cycles in them, and you are only increases that number. It is a good idea to charge the phone whenever you can, then about once every other week go ahead and let it drain then charge.

I agree except letting it drain every other week. These are Lithium Polymer batteries, which you should simply try to keep juiced when possible. Apple's own recommendations are to let it run down about once a month.
Personally, I keep my phone charged when possible, and it stays on the charger nightly. I reboot every 3-4 days, and I average about 4.5 hours of use, playing a LOT of Tap Defense, text, and wifi browsing. I am sure that I could probably squeeze another hour and a half out of it, but I won't let it run down that low as it is advised to be bad for the battery.

more info here: http://www.maxamps.com/lipo-care.php

[JoeT]

In the world of RC Cars a slow charged battery will last longer than a fast charged.
So there may be something to the thought of charging slower resulting in a better charge, that in turn will last longer.

What you are referring to is a "quick charge" in which the charger throws as many amps down the battery's throat as it will take without exploding.

That results in a lower net charge due to the effect of the increased heat that is generated on the battery - which is neither the same as the battery's capacity diminishing nor anywhere near the type of charge rates we are discussing at 500 vs 1000 mAh.

Quick charging can shorten a battery's life dramatically, but neither charging method for the iPhone would be considered quick charging.