I drain out about 1.25 gallons of coolant at 100k miles and then every 50k past that. Seems good enough in my Toyotas.
Without data you're just another person with an opinion. W. E. Deming
2003 Corolla 250,000 miles (RIP)
2004 Corolla 125,000 miles
2004 Rav4 392,000 miles
2015 Camry 90,000 miles