Standby battery life is pretty good. However if you use the phone a lot expect to see diminishing returns real fast. the most I've got is 5 hours over WiFi but I believe it's possible to get more mileage. Though that would IMO involve the crippling of the phone functionality

Sent from my Nexus 5 using XDA Free mobile app

kwPhone6: Google Nexus 5 D821: Android 4.4.4 Stock ROM, Franco kernel r63, PhilZ touch recovery
kwPad2: LG G Pad 8.3 V500: SlimKat 4.4.4 Linaro (Infected_ build 7.9), PhilZ touch recovery
kwPhone5: Galaxy S III i9305: SlimKat 4.4.4, PhilZ touch Recovery

---RETIRED---
kwPad: ASUS Eee Pad Transformer TF101, kwPhone4: iPhone 4, kwPhone3: Samsung Tocco, kwPhone2: Nokia N73, kwPhone: Samsung SGH-X680