I have had my iphone6s for 4 months. I was amazed at first as to the battery life. But now it's already at 40% only 2.5 hours into the day. Of which I have probably used the phone for half the time and only e-mail and web. I don't think my use is different. I did leave it plugged in for 2 weeks while I was out of the country and it seems since then I have noticed the difference. Any advice on how I can check the battery condition or anything to do with my phone? Of course I have restarted it and closed apps.