If more than a day has passed, and we still do not get data from the sensor, we invalidate the connection, and remove the annotations we have stored for the corresponding roster item:

else if (SecondsSinceLastEvent > 60 * 60 * 24) 
{ 
   if (!string.IsNullOrEmpty(this.sensorJid)) 
   { 
         Item = this.xmppClient[this.sensorJid]; 
 
         this.sensor = null; 
         this.sensorJid = null; 
 
         if (Item != null) 
         { 
               this.xmppClient.UpdateRosterItem(this.sensorJid, 
                     Item.Name, this.RemoveReference(Item.Groups, 
                     "Sensor")); 
         } 
   } 
 
   Search = true; 
}