queryStatus storage duration for cleared alarms

Does anyone know how long cleared alarms remain in the internal alarm system? Particularly when using the system.alarm.queryStatus() function and looking for 'clearUnacked' or 'clearAcked' states? Forever...or until a gateway restart...or 7 days? I know the journal is stored in an external database and has settings in the gateway for that...but I am referring to the internal alarms table.