How long is a Kubernetes minor version usable on EKS before it is forced to move?

Why this is the answer

A minor version gets 14 months of standard support, then 12 months of extended support at an extra per-cluster-hour cost, for 26 in total. Extended support is on by default and can be disabled, which converts the cost into a deadline. Planning the upgrade cadence against 26 months rather than 14 is what keeps a cluster off the forced path.