It was a little over a week ago that we received a new update for the Transformer Prime. That one was version 220.127.116.11. Today, an incremental update, which is version 18.104.22.168, is rolling out to users OTA. You can click on Settings -> About tablet -> System Firmware Update -> Check Update to manually check for it. Gary Key, Technical Marketing Manager at Asus had this to say about it just yesterday,
The update returns the lower power states features (such as when the device is idling). Several users have reported that this results in better battery life. Keep in mind that this update does break root, so plan accordingly..14 will be released tomorrow (US/TW, WW/DE/Others early next week), should solve the power problems that some users experienced after the .13 update.