Many people (admittedly of the slightly older generation) don't need to be constantly connected to their email. Addiionally, those from the Palm generation are OK with syncing their calendar and contacts at the end of the day rather than needing constant sychronization with Outlook on their computer. Well. I found that if you turn off synchronization of with an Exchange Server over WiFi, the battery charge depletion crawls to zero (for all practical purposes) when the phone is put to sleep. For this to happen, one must have disabled data usage and ensured that WiFi is automatically disabled during sleep mode. I use CyanogenMod 12, and the battery depletion tracking gave a projection of umpteen days before depletion, as opposed to 1-2 days before I turned off syncrhonization. I could see the marked difference in the plot of the battery charge with time. The funny thing is that before synchronization was disabled, I still had data usage turned off, and WiFi was set to be disabled whenever the phone was asleep. The only thing I can imagine would burn up battery charge so voraciously is CPU activity. Maybe the synch routine is CPU intensive. Who knows.