I have no doubt that others have said this before, but wars to install a pretender should not end on the person's death if the claim is inherited by a person who it is either valid for you to press the claims of, or can be made so immediately (e.g., will accept an invitation to your court). The war would still end if no one can inherit the claim, or if you can't install the claim inheriter (from another court and won't come to yours, is a different religion, etc.). It doesn't make sense that everyone would just give up and go home because the guy died if he's got a son: the fact that they're waging the war at all means that they believe he should be on the throne, and therefore the succession rules should still apply.