Mean mantle temperature for different models of 55 Cancri e with different rates of internal heating and constant or decreasing CMB temperature. The dashed lines indicate models that include decreasing CMB temperature due to core cooling. Solid lines indicate models with constant CMB temperature. The mantle temperature stabilises after around 1 and 4 Gyr for the models with high and Earth-like internal heating, respectively. Without internal heating, the mantle temperature will continue to decrease beyond 4.6 Gyr.