At the very least you will need another little robot or human that goes by and verifies that the prices have actually been updated. I can't imagine the LCD price displayers will be super high reliable and built to last decades.
You seem to think that electronic price labels is a new unproven technology, while it is actually extremely common and well tested. After the initial introduction period, where errors can occur, it's pretty much guaranteed to work as flawless as it does everywhere else.