If you are able to setup your dynasty members in a good separate realm it will never ever be game over. When I originally set my brother (Italian) up a hundred years ago in Sweden. I had to constantly bail him out of trouble for over 50 years until his Swedish heir finally took over which calmed all of his vassals. But now he always sends between 5k and 8k of troops when I call him into battle.
Elective is very useful when you have created separate dynasty branches in other realms.