I use a 2600mah. I keep it as a backup spare when I am running around. I normally stick to stock battery. Since using EWJET 2.1 custom ROM, my stock battery will last me just over a day so I never bother using the 2600mah as much. When I do use it, I can run it over 3 days. I do make over 2-3 hours of phone calls a day.