Egos are usually rated as good for 300 charges (that's full charges). That being said, I've had one last 2 months and one last over a year. I've had 2 that the buttons stopped working properly (one of those because I dropped it on a concrete driveway)...and then there was the one I accidentally put in my full cup of coffee. (I swear I thought it was empty). However long they last, you can never have too many backups.