So I'm Aragon and Napals broke free. So I got this casus belli and crushed them... king died AGAIN before I can bring up my prestige. I have to wait 4 more years for this truce to end. Should I break truce?
You can also always check the ledger. The Casus Belli page lists all the ones you have and when they expire (if they do).
Don't think its prestige anymore causing break on death but relations.