So, to summarize I've found that with windows 10 mobile (.36) the battery life is initially better IF your not actually using the phone. I would lose only about 1% overnight at first - great standby. Then after about a week it would lose about 4% overnight. Estimated battery life after full charge went from over 5 days at first, to 3 days. The culprit in the loss of battery % is most definitely "Skpe & Messaging", confirmed buy not using phone for 24 hours and looking at battery usage - literally all battery usage was from it. Thing is, I've unlinked my account from Skpe - even went as far as deleting it, but makes no difference. I don't even use Skpe and I bet most users don't either; Microsoft should impliment an option to un-intergrate it from messaging altogether. What has made me go back to 8.1 for now is my 1520 would heat up at the top while playing candy crush and while sucking the battery at a super fast rate. Pretty much all I use my phone for is Candy Crush, texting, some web surfing/videos & ocassional phone calls & right now 8.1 does a better job at that. Windows 10 mobile is better visually and is very close to being better than 8.1, but not quite there yet for me.