Or your heat exchanger at the same time….Fear of trail failures caused me to pay to have it done preemptively along with water pump, thermostat, alternator, idler pulley, tensioner and belt at 128k or so… and it was expensive… but the 1000 yard stare from the seasoned tech when I picked it up told me it was well worth it and probably less than the years of therapy he would need to work through the trauma from doing both the alternator and starter at the same time.