The sample code below adds a Name/Value collection of 10 items (a most recently used list) to the XamRibbon's application menu's recently used list.  After running this code a dozen times, the time to complete the line

        PentaRibbon.ApplicationMenu.RecentItems.Add(buttonTool);

increases to about 1/2 second per call.  Is there any know bug with this?

    private void UpdateMRUList()
    {
      PentaRibbon.ApplicationMenu.RecentItems.Clear();
      foreach (ExtendedProperty extendedProperty in _mruList.Screens)
      {
        ButtonTool buttonTool = new ButtonTool();
        buttonTool.Click += new RoutedEventHandler(buttonTool_Click);
        buttonTool.Caption = extendedProperty.Name;
        buttonTool.Tag = extendedProperty.Value;
        PentaRibbon.ApplicationMenu.RecentItems.Add(buttonTool);
      }
    }