After looking at the Rainlab User plugin I understand that to be able to listen to a plugin's events you need to register them from within the plugin that you're extending (Event::fire()). That means customising the plugin's code which makes you vulnerable for problems when plugins get updated. Isn't the purpose of extending that you protect your code against that kind of stuff? I guess the question is, is there a better way to register events without having the risk to loose work on updates?