I found this thread but its pre-patch
Re: Game over too quickly
How can this be prevented to make a more challenging and longer lasting campaign?
There are a few methods:
1) Add a few extra Royals and 'bend' history slightly i.e Add Rupert/Maurice syblings and make Charles II 4 years older.
2) Add high ranking commanders such as Astley or Hopton to the family tree.
3) Remove the family tree altogether.
Would it be possible to get AI faction leaders to look after themselves better, either by avoiding battles or staying out of trouble during battles?
This is something I'm working on.
Cheers