I don't change my antifreeeze until I know it won't work like it should. I use an antifreeze tester to check it 2-3 times a year. they cost about $4 on amazon or the same a walmart
https://www.amazon.com/Prestone-AF-...ocphy=9030236&hvtargid=pla-570724898553&psc=1
https://www.amazon.com/Prestone-AF-...ocphy=9030236&hvtargid=pla-570724898553&psc=1