I bought this battery when I bought my Pentax K-7. I keep both the original battery and this battery in my camera bag. I take tons of shots when I'm out with my camera (normally at a zoo, car show, etc.). Since the K-7 uses battery packs instead of disposable batteries, if the batteries run down, my photography day is over. So far I've shot all day with one battery on a full charge without any problems. This battery just keeps going! I don't worry about whether I'm using the flash or not, as this battery has enough power that it's never been an issue.
It's good enough that I've not bothered buying the external battery pack for my camera.