The valid lifetime for each type of route is updated (extending the life of the route) by the periodic receipt of router advertisements as long as the sending router is available and is not reconfigured relative to its defined prefixes or default router status.

When a Prefix Information option contains the Valid Lifetime value infinity, the implicit or prefix route associated with the public autoconfigured address is considered permanent and does not age unless a future Prefix Information option for the prefix contains a Valid Lifetime value that is not infinity.

Expiration of the valid lifetime for a default route is immediate if a future router advertisement indicates that the sending router is no longer a default router. Expiration of the valid lifetime for a prefix route is immediate if a future Prefix Information Option for the prefix contains the Valid Lifetime value 0 or if a future Route Information Option for the prefix contains the Route Lifetime value 0. The valid lifetime for an implicit route cannot expire immediately because the minimum lifetime allowed is 2 hours; the lifetime must age out naturally.