SUMMARY: Source expiry marks the point where a once-useful reference needs review before it can keep carrying authority.
Links age. Reports shift. Pages move. A reference that helped readers last month can mislead them later if the surrounding context changes. Source expiry does not mean the source is bad. It means the operator should stop treating it as automatically current.
The archive becomes stronger when old evidence is allowed to keep its date.
Expiry Signals
Link change: a source redirects, disappears, or changes its title and summary.
Context change: the event, policy, tool, or public claim has moved since the reference was captured.
Authority creep: an old citation starts doing more work than it was meant to do.
Reader risk: outdated information could affect a decision, account, safety setting, or public interpretation.
Operational Use
Use source expiry with link custody. Link custody preserves the route. Source expiry decides when the route needs a fresh witness.
Operator Rule
When a source keeps influencing the map, check whether the source still says what the map thinks it says.
Field assessment: stale evidence should be labeled before it becomes invisible authority.