This read-write TruthValue turns off automatic aging of dynamically learned MAC address entries on a Transition Networks switch. An admin sets this to true when they want dynamically learned MAC entries to persist indefinitely rather than expiring after the configured aging time, useful in stable topologies where entries rarely need to be relearned. For example, setting this to true on a fixed backbone link stops the switch from aging out that link's learned MACs even during a temporary traffic lull.