Have you ever taken flash photos and it takes for ever until you can take another picture? What is going on is your flash is dumping so much power that it takes longer for your batteries to recharge the flash to fire again. One of the major reasons that your flash is dumping so much power is your ISO is set to a lower number.
We know that when your ISO is set to a lower number that you need more light to capture the image. The same thing happens with the flash, when you use low ISO your flash has to dump a lot of extra power in order to expose your image sensor properly.
If you would like to use less batteries and be able to shoot flash photos quicker, bump the ISO!!!! When you bump the ISO your camera does not need as much light meaning that your flash will not have to dump as much power allowing it to shoot faster.
There are some other benefits of raising your ISO when you are shooting with the flash such as being able to light subjects at a further distance and a simple thing of using less batteries over time.
I hope this quick tip got you thinking about your own flash photography. Be sure to test it out for yourself and see the difference.