Charging your iPhone overnight won't affect them negatively in the slightest.
Answering a question on Quora, tech writer Jesse Hollington refuted recent reports that overnight charging does lasting damage.
"You simply can't overcharge an iPhone, or any other modern electronic device, for that matter," wrote Hollington. "When your iPhone is plugged in and reaches 100%, it switches to external power and simply runs from that."
The explanation is that any device that uses a Lithium Ion or Lithium Polymer battery must incorporate a charging circuit that cuts off charging power when it hits 100%.
Hollington went on to add that charging your battery before it's fully depleted is actually the preferable way of doing it, because of the limited number of 'charge cycles' for a Lithium Ion battery which is about 500 in the case of an iPhone.
He explained: "Every time you charge your iPhone up from 90%, you're using 10% of a complete charge cycle. This means you could charge your iPhone up from 90%-100% 5,000 times before you'd have to worry about running out of charge cycles.
"However, if you deliberately drain your battery to zero and then recharge it, you're needlessly using up a complete charge cycle. Obviously if you're using your iPhone until the battery goes dead, that's fair, but there's no need to deliberately drain it before recharging it, and you'll actually shorten your battery life if you do so."
That'll be music to Apple's ears given the recent issues with their iOS 9 roll-out.
And it'll make the record-breaking number of people who have ordered the new iPhone 6S and 6 Plus even happier.