How to manage lifetime of dynamically allocated QObject derived objects passed to QML?

What worries me is the fact the echo() slot is never triggered. Not even as the application is closed. This leads me to believe such objects returned to QML are practically leaking, and I am not a big fan of believing somehow this is not the case. I don’t like memory leaks. And somehow QML seems to be full of those. I’ve already encountered situations where QML doesn’t release resources and memory usage climbs to hundreds of MB and never drops down.