Nb: Some of my "Butcher Grandpa" got battle weary too... but their ancillaries and other traits seemed enough to counter these effects effectively... I think you'll got battleweary more often if you use them on advantageous / balanced battle and lost... putting yourself at small disadvantage (especially in numbers), will give them nicer traits...

Anyhow, using "Butcher Grandpa" seems to had a nice portaits of family tree, as only the most of scarred, the most berserked, and the most mad died in battle (not surprisingly)... and when they reach 65's I will pick up nice Military-talented Highschool Boy (often their nice and peaceful Grandchildren or great grandchildren...) to step on their Grandpa's madness Most of their dynasty though, worked as 1-2 starred FM with 3-5 influence and management skills...