Thanks for good suggestions. Scheduled Power On/Off seems like a good workaround, but in my case it does not work as expected. It does power off the device but fails to turn it back on. I found that simply connecting to the charger turns the device back on.
My $400 investment is barely 7 months old and progressively falling apart. The power button stopped working after a series of strange behavior, like "Charging other device via USB" notification, not responsive "Smart Key", random launch of applications set to be opened with the smart key. (Honestly, I have serious concerns about build and components quality of Huawei products.) Regarding water damage, I don't think this is the case. The device was never exposed to liquids. Also, I would expect it to be engineered as sweat and humidity resistant, which may not be necessarily true.
I wonder how many Honor 8 customers experienced issues related to water-, dust- or heat-damage, without actually abusing the device.