Perfect answer Hob.
Anything deriving from UIComponent will take a long time to generate the proxy as it has hundreds of methods and accessors. And this happens for each separate UIComponent-subclass that you give to Mockolate.
I am considering a feature to allow specifying which methods should be proxied, however even if this feature was available now I would strongly suggest using interfaces instead. Consider using IUIComponent or IVisualElement, or something custom depending on your requirements.
cheers,
Drew