It is, but only temporarily. Will you switch it over to a heat pump immediately after the cut off point is reached or will you operate till the end of its life

It is, but only temporarily. Will you switch it over to a heat pump immediately after the cut off point is reached or will you operate till the end of its life before you replace it? If you keep operating it, will it really emit less over its lifetime than switching to a heat pump right now? Making the assumption that today's electricity mix is a steady state is flawed.