It all depends on how the phone is used. In my case, with a Nexus 4, the battery life is an issue. When traveling, I will often take multiple photospheres (comp

It all depends on how the phone is used. In my case, with a Nexus 4, the battery life is an issue. When traveling, I will often take multiple photospheres (computationally expensive). I will use it to do research on where I am visiting (lots of screen use). I use it for general browsing (more screen use). And in those scenarios, I rarely can go a full day without charging. That said, it seems the portable chargers are the preferred way now. They often hold enough charge for 4-5 phone charges, so that is nicer than carrying around 4-5 batteries. And, I can charge lots of other things with it as well.