Isn't it more like "Bingo: now I have a battery pack dangling from my phone for the next few hours"?
I used to own a battery pack too, back when I had an iPhone, it was a required accessory unfortunately. Since then I've owned a Samsung Note (1), LG G2, and Sony Z3, and all three of them last 2-3 days, and I have no need for a battery pack.
Even if size was a concern I could purchase a Sony Z3 Compact which is "iPhone 6 sized" but has twice the battery life or more.
Back in the iPhone 4 (ish) day the iPhone had "impressive" battery life. However Apple has stood still while everyone else has continuously improved. Now most non-Apple phones (Galaxy S5, LG G3, Sony Z3, Note 4, Windows Phone, etc) last substantially longer than Apple unless you're buying an unbranded piece of junk.
So I found a remarkably simple and obvious solution: I spent £50 and bought an external battery pack, something like http://www.amazon.co.uk/RAVPower-15000mAh-External-Generatio... . It charges overnight, weighs not all that much at the bottom of a shoulder bag, but on those crucial days when battery is getting slim, I can just pull a cable out, plug it into my phone, and bingo: the phone is charged.
It's capable of charging an iPhone several times over so easily solves the problem for you and even some of your friends.