Not sure what works for you, but I remove extra stuff on the phone. Eg don't use the google search stuff, so I removed that, the same goes for htc watch, reader, stock, twitter, google voice and all the other apps I Don't use. Used Titanium Backup (payed version, gives option of freezing apps). And then I guess radio and provider also has a thing to say. where I work I can throw a stone at my providers nearest antenna. So most of the time, I'm close to excellent coverage. Also I try to keep my phone on wifi as much as possible, since it uses less power keeping a connection.
Also at night I use display brightness to a minimum.
It whas the free version and i didnt freeze them but then again it gets deleted so why should it be frozen?
As for the screenbrightnes i already have it at manual so nothing i can do there
Sent from my HTC Sensation Z710e using xda premium