Battery life is around 1-5 hrs. It's not consistent. Sometime I do nothing, and the battery drains in an hour by itself. Sometime, I do light browsing and get 2 hrs. More often, I get ~5hrs, maybe a little less. I don't trust the battery life indicator one bit. It's so unreliable. I clock the battery life myself. It's a shame that a company that makes the OS can't get power management right. They should just license the technology from Apple or Lenovo. Back in the Windows XP, during the dark days of battery life, Microsoft was actually ahead of Apple but behind Lenovo. Now, they seem like years away from both.
Battery life, heat, fan, and crashing video drivers are the only remaining problems I have with the device, but these are huge problems. The camera not working, video flicker, and audio popping have all been fixed since the latest firmware. I have a feeling battery life can be stabilized in time. The standby time of 24hrs will never be as good as a Mac where it is 30 days. I worry the heat and fan is an artifact of the battery chemistry. Batteries heat up during charging. Maybe the fan powers on to cool it down. The likely fix might be to slow down the charging rate.
Don't bother bringing these to the Microsoft store. Unbelievable denials - "huh, I haven't heard this yet, maybe it's your device. Maybe we should trade it out." or "Maybe you should do a full restore". How about maybe I don't waste more time trying to pseudo fix the problems with your company's crappy software?