The effect of the applied trajectory length on the convergence of the static dielectric constant was examined for the SPC/E water model with different system sizes. Very long simulation times of 6-8 ns were employed in order to track the convergence of this property. Temperature dependence and isotope effects were also investigated. A simulation for the polarizable SWM4-DP model was also carried out to compare the effect of different potential models. It is clearly shown that trajectories shorter than about 6 ns are not sufficient for a sufficiently accurate determination of the dielectric constant of these water models. (C) 2011 Elsevier B.V. All rights reserved.