Few important point regarding event registration.

If an instance triggers an event, the registration is implicitly deleted if the triggering
instance is deleted by the automatic memory management (garbage collection).

When you register instance methods as event handlers, note that the registration refers to the current instance and not to the reference variable that is used for registration. Even when the reference variable takes another value after SET HANDLER, the registration of the object remains unchanged. This also affects to the lifetime of objects - an object exists for as long as it is registered as an event handler, even if no more reference variables point to it. The object is either explicitly deregistered using the ACTIVATION addition, or implicitly when the triggering instance no longer exists.