What if you went camping?
Well, I have backup batteries, but, still, it's a valid point. Especially if you are using your GPS and you don't have back up batteries.
Sure you can charge your phone overnight, but, I don't see how improving battery life is a bad thing. The battery will last longer, you'll save electricity, and, if you are using your phone really hard it'll last longer. I can blow through my phone battery in a couple of hours if I am using it really really hard. So, anything that can improve it is a good thing. Generally I get a full day out of my phone, but, on the off chance that I need to use it really hard during the day, having it run more efficiently and last any amount longer is a good thing, IMO.
I mean, there is nothing wrong with discussing efficiency, right? You can fill your car up with gas when it's almost empty, but, wouldn't you still want to know how to get better MPG?