For the record, the upcoming Lenovo Mirage Solo headset has a 4000 mAh battery and (purportedly) 10-hour battery life. Of course, it is double the price of the Oculus Go.
it looks like it is available now: https://www3.lenovo.com/us/en/tablets/virtual-reality-and-sm...
[1] https://arstechnica.com/gaming/2018/05/oculus-go-review-the-...