Cool, I have my mind made up: always ON. It's a fantastic option, really. I switch off the device when I'm not reading for 4+ hours, anyway. Otherwise, I'll leave it on, ready to read instantly.
Option to set the standby time is yet another feature giving this device advantage over Kindle. [Though I'm still attracted to DX's large screen for those PDFs.]
Jellby: Friend of mine who got one of the first CyBook Gen3 devices already bought a replacement battery and is furious how little it lasts.
Elena: Ah, yes, that's a great workaround. It's good to know the life-span of the device is thus not limited to replacement batteries being around.