OEM coolant has a 10 year life.
Nulon says 6
Tectaloy says 3
Havoline don't state for theirs but say it was still good for purpose during testing after 250,000 kms.
Had mine changed recently as I was not certain how old the donor motor was that went in 4 years ago. Following that the coolant outlet housing started a slow leak and then spat the dummy when given a pressure test.

