Using Lumia 525, my daily average use (Battery Saver always On, brightness Low):
12am-10am (sometimes until 12pm or later, depending if I'm too busy at work)- Flight mode On, no apps open
12/1pm - On Wifi, open Whatsapp and Nokia Xpress/I.E for about 20 minutes
1pm-6/7pm - No usage except for occasional quick Wifi use if got spare time.
6/7pm-10/11pm - Wifi on (not constantly but most of the evening), Whatsapp running
By end of the day I'll have used about 15-20%
BTW is Instagram Beta for WP 8.0 suppose to drain battery even when its closed?
Use 6tag for instagram.. better