How long does the quantum chaos last?

The main purpose of this Comment is to point out that besides the short time scale of quantum chaos, confirmed once more in recent paper by Alicki et al, there is generally another time scale t_R, which is much longer and on which a partial quantum-classical correspondence persists. Namely, the quantum diffusion closely follows the classical one even though the former is dynamically stable. The absence of the long scale t_R in model studied by Alicki et al. is a result of a special choice for one model's parameters value.