My first couple of weeks was rough. First week or so i could not get more than 6-7 hours. I have Lumia 920 since Dec 13th, and last week my battery life is much better. Sometimes I can go two full days without a charge, all with using Whatsapp and Viber frequently, 25-30 regular text messages a day, 30 min of talk time, location on, brightness on medium, int explorer 1 hour, and WP central and store usage few times a day. I really cannot complain now, but it took some time to get to this point.
Today I had an interesting case with battery life. Battery was at 47% then I turned the phone off and immediately on and it dropped to 35%. I kept using it and it went down to 16%. I turned it off again for a couple of hours and when I turned back on percentage was at 28%. Anyone had a similar case?