Throughout the JSF framework, UIComponent objects delegate behaviours to their Renderer, which is accomplished in UIComponentBase by:

    Renderer result = context.getRenderKit().getRenderer(getFamily(), getRendererType());

The call to FacesContext.getRenderKit() takes up the majority of acccessing the Renderer. In JSF 1.2, their FacesContextImpl class does the following for getRenderKit():

     private RenderKitFactory rkFactory;
     private RenderKit lastRk;
     private String lastRkId;

     public RenderKit getRenderKit() {
         assertNotReleased();
         UIViewRoot vr = getViewRoot();
         if (vr == null)
             return (null);
         String renderKitId = vr.getRenderKitId();
         if (renderKitId == null)
             return null;
         if (renderKitId.equals(lastRkId))
             return lastRk;
         else {
             lastRk = rkFactory.getRenderKit(this, renderKitId);
             lastRkId = renderKitId;
             return lastRk;
         }
     }

Ours is implemented a bit differently, which brings up questions of correctness. But, regardless, the key optimisation involves caching the last RenderKit, as well as the RenderKitFactory.