I rarely need it but I have an extra Samsung battery and charger as a backup. I just swap out batteries if I'm away from a charger for an extended period of time.
+1 on Lucy D comment.
However, I bought 2 Anker Li-ion 2600 mAh batteries that work very well...as well, if not better than the OEM battery. (I would guess that the average user can probably get a day of juice from it. Me? Not so much. I'm a heavy user.)