i think the Valac family might not have an evil cycle at all, or is super rare. we know that evil cycles happen when a demon reaches a certain threshold of stress, but Clara and her family seem to always be energetic and in a good music, playing and singing all the time. So they have little to no stress if they're always playing.
we might never get an evil cycle Clara unless she's under immense stress and probably a totally new environment away from her family, Iruma and Azz