If you have only one slave flash or are using only one group, it's easy to shorten the preflashes. There are benefits to doing this: extending battery life slightly, preserving the operating life of the popup flash, and most importantly, reducing the likelihood of blinks.
To shorten the preflashes, all you have to do is disable the unused groups (Group B and C if your slave is in Group A). Disabling a group is done by selecting "--". You'll notice the commander preflashes will become shorter than if the unused groups are active.
If you liked this tip, you may be interested in the SG-3IR, which can reduce blinks.