But that's not what's happening here. If anything, it's driving the e-ink display less. The main risk is that grays are not well-defined. Given a pulse train to get a certain gray level, that gray level might change over time due to aging of the e-ink panel, or it might change directly with temperature or other environmental factors.

Another issue I heard, but I don't know enough about the physics of e-ink to know if this is correct, is that if you are at a gray level, the white and black particles are mixed and might exchange charge, thereby causing some particles to not move correctly anymore.