Losing css changes on Panel each time the panel contents are destroyed

Hello Experts,

I have a Panel and all I want is I do not need the header in 2 Panels in my application. For that I have used the below line in onAfterRendering method in controller.

onAfterRendering: function() {

       $('#oPanelDates-hdr').css({"background": "none"});

       $('#oPanelAddRowSave-hdr').css({"background": "none"});

   }

The 1st time the application loads, this looks perfectly fine. But as soon as I destroy the Panel content, I have the header back.

Which hook method do I use as I want this to be permanent despite navigation, or any changes made in the Panel.

I have tried the above piece in onBeforeShow() as well

Thanks & Regards,

Archana