I have a standard battery with a 2 minute delay on the display blackout/lock and do as you do - manually lock it before the 2 minutes kicks in. With heavy usage, I'm generally at about 30-40 percent by day's end... but with a regular battery.
The display is usually the greatest power hog. Wondering if you have some widgets that update frequently. Some are way more power hungry than others, for instance any "news" widget. Check the refresh rates for these and lower them - see if that makes a difference.