Despite the smaller cell under the hood, Asus claims that their Zenfone 3 Max is capable of delivering 20 hours of 3G talk time, 20 hours of 4G web browsing, hours of video playback and a whopping 30 days of standby battery life respectively. (techpp.com)
Marshmallow introduced Doze Mode, which greatly improved standby battery life by putting your phone into a deeper sleep mode when your screen was off, the phone was unplugged, and the device was lying flat and still. (android.gadgethacks.com)
Some Nexus 6P owners on the AC forums have been seeing significantly reduced standby battery life on their phones. (androidcentral.com)