My usually average use time of Samsung Galaxy S3 last 13-15 hours because of the heavy way I use so I had to get an extended life battery...I have a lot accounts syncing, and I am always playing games, browsing the website, using GPS and YouTube videos.. My friend on the other hand gets almost one whole days out of his stock battery, so every user is different. Surely 13-15 hours fall short for me. So I really needed to get an extended life battery... and last week I got a MPJ replacement battery for my birthday! And now I also got a whole day even though under heavy usage and even a little longer after calication. I aslo download the Android App “Battery Left” to see accurate battery life readings for the new extended battery, and I am glad to find out these great diferences.