What are you doing where it's unusable with a single charge? Most days I get by fine or mostly fine with my phone and I'm a pretty heavy user (music, web browsing, fb/twitter/instagram).

I had to get an external usb battery but only use that when I know I'll be busy a full day with more than usual usage (which is still quite a bit). Example being a full day of work (commute in and out) plus a sportsball game at night or similar where I'm seriously out all day.