I wouldn't bother. Since ICS and now Jelly Bean, Android is very efficient. It has been proven many times that task killers like Juice defender just introduces issues with little benefit. I used it on older phones like the TBOLT and Razr, it worked wonders, but once Razr updated to ICS it was a mess. It just didn't work smoothly and I could never figure out if it was juice defender or the phone. I didn't even bother for the S3. I would just turn on power saving and keep a spare $9 battery in your pocket just in case.