I am not an expert on batteries, but I wondered both at the time and now if the desire to shave another millimeter or 2 of thickness off of the phones would impact battery life in a couple of years. I use Lithium Ion batteries as backup power in a lot of the machines that our company designs, and size definitely relates to service life for industrial equipment. As I stated before (in another thread?) I don't know the quality of the battery supplier Apple uses, and I have no idea what the standard (real) life is for most smart phone batteries, so I don't know if Apple is better, worse, or about the same as far as battery longevity is concerned. And I mean how long they really last, not how long Samsung, LG, Motorola, Google et al. claim they last.