I have an iPhone 6, which has been a great phone, and I'm wondering if there is enough improvement from the 6 to the 7 to upgrade. I know that lithium ion batteries only have a limited number of charge cycles - I understand it's around 500 - and I'm guessing my iPhone6 will start to slow down as the battery gets to this limit sometime in the next year or so. That's what happened to my old Pod Touch - slowed to a crawl and wouldn't hold a charge for very long. If I were to trade my iPhone 6 in now on an iPhone 7, while my battery is still good, I could get a much better trade-in value from Apple than later, when it's running slowly. Of course, I would wait 2-3 months before trading in, to see what kinks get worked out in the new phone and iOS10. What do you think - worth upgrading?