Modern permanent magnets show an irreversible increase of the remanent magnetization for increasing temperature. This thermal remagnetization (TR) occurs after DC-demagnetization at the initial temperature T0 followed by heating. The TR is especially large for well-aligned sintered SmCo5 permanent magnets and is strongly correlated with the grain-interaction and the temperature coefficient of the coercivity. We present a systematical study on the influence of the initial temperature T0 on the TR of SmCo5 sintered magnets experimentally and theoretically. We find that the TR-maximum increases with decreasing T0, whereas its position Tmax shits slightly to lower temperatures with decreasing T0. This together with the dependence on the sample demagnetization factor N, is in agreement with the results of our model calculation.