I’ve had my Nexus 5 for about a year now. Device is fully up to date. I run minimal apps to save battery power. I woke up this morning at 7am, unplugged my phone with a "full" charge. It’s now 1:15pm and I have 9% & "Power Saver" on. What have I been doing all morning? Watching full length films perhaps? No. Listening to music for about 2 hours at school with the screen OFF, and WiFi OFF.
In the last month or so since the OS update my phones been complete garbage. Which is sad because it look great and performed very well for the first year.