The wavelength dependence of convection with a temperature dependent viscosity is studied using two-dimensional finite difference models. A steady state solution with a horizontal wavelength of eight times the depth is found to transport heat more efficiently than a solution with exactly the same parameters but with a wavelength of twice the depth. Only at the longer wavelengths (&lgr;>8d) is it possible for the top high viscosity boundary layer to participate more fully in the flow. Since models with a constant heat flux were used this resulted in a decrease in the interior temperature of approximately 30% for the longer wavelength. It is also demonstrated that a parameterization using only a constant viscosity thermal structure and an interior viscosity is inadequate to parameterize the variable viscosity calculations described in this study. This suggests that parameterized convection schemes may not accurately resolve the thermal evolution of planetary interiors unless they can correctly include the effects of vertical viscosity structure.