Hi, I don't know if this has been asked before, I couldn't find anything... Whenever I install a new iOS update, battery life on my iPhone 6 is fantastic. Even with quite heavy usage I still have 30-40% left at the end of the day. But that changes over time. After just a few weeks, the battery will drain a lot faster and I need to charge the phone much earlier. This always happens after a few weeks but is temporarily fixed when a new iOS version is released. It was the case with 8.3 -> 8.4, 8.4 -> 8.4.1, 8.4.1 -> 9.0 and so on. It don't change any settings (background activities etc) that could decrease battery time nor did I install a ton of new apps. Any ideas what the problem might be?