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I don't have to. My phone usually lasts 2-3 days on a full charge. But it fits into a pocket in my laptop bag quite nicely, so I always take it with me so I can top up my phone at work if I want to.
 
Nope. My 6+ lasts me all day. For example, today I got to work at around 2:00. Didn't get home until midnight. Phone was on 75% battery when I plugged it back into the charger by my bed.
 
I leave my charger at home as my iPhone 6 easily makes it through 1-2 days on a overnight charge.
 
One full charge on my 6 lasts me about a day, so I'll charge in the evening. I do carry a cable in my work bag in case I do need a charge.
 
I do keep one on me in my breifcase in case of emergencies. However, I don't really need it. It is just good to have.
 
I always bring it regardless but since I got the iPhone 6 I haven't had to use it. With my 5S the battery used to be near dying by around 6pm (from fully charged at 7am).
 
Yes. For some reason being in Chicago makes my battery drain faster than at home. Probably has something to do with the cell service.
 
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